@robertGL I've only a little experience of using VP15 but I would say that it you use a GH5 then it is worth upgrading because "4K, 10-bit 4:2:2 AVC files from the Panasonic GH5 camera are now supported" .
From the readme file these are the features which are significantly useful to me: A new MAGIX AVC/AAC codec significantly accelerates encoding on (a) machines that utilize Intel® Quick Sync Video (QSV) technology (b) machines equipped with modern NVIDIA graphics card GPU technology

The user can now select from the list of attributes of a copied timeline clip event to specify which attributes will be pasted into a target event. (Useful but not as fully implemented as the corresponding feature in Resolve 15).

There are a number of other small changes and lots of bug fixes (some even post the release of VP 16).
Some of the hitfilm essentials FX also included with the deal are useful if you don't already possess similar FX. So there isn't a huge difference but $25 is not a lot to ask and the offer is only around for about another week.

The third update for VEGAS Pro 16 !

You can download the build 352 now at: http://rdir.magix.net/?page=CSKN58Y07E4C

Features

• In addition to manual refresh to keep the storyboard in sync with the timeline, an automatic refresh option has been added so the storyboard refreshes after each timeline edit
• An update notification feature has been added in order to keep in better touch with users when new product updates and fixes are available
• DX12 based HDR external preview support
• The video stabilization plug-in now has three modes for use depending upon the level of control desired ranging from basic mode with simple one-click operation, to expert mode with a powerful set of optimization parameter controls
• Automation for Video stabilization parameters enables you to make adjustments over time or to bypass stabilization during certain portions of a clip
• HDR Mastering Display Metadata for rendering HDR10 content has been added to the Project Media window
• A filter option in the Render As dialog box filters the render formats and templates down to just those are are 360° compatible when you've specified your project as a 360°in the Video tab of Project Properties
• Mechanism is now in place to inform users when a new update of the software is available

Bug Fixes

• Inconsistencies when analyzing a video for stabilization with the Static setting selected have been resolved
• Closing and reopening the Project Media window no longer disengages storyboard hover scrub, and no longer resets storyboard in/out points
• Stabilization works properly when the video is contained on a track that has an audio track above it on the timeline
• Using the Esc key while dragging an event properly cancels the move operation rather than clearing the storyboard and causing a crash upon reopening the Project Media window
• The mouse wheel works properly with OFX plug-ins even when Scroll Inactive windows is enabled in Windows
• This update correctly preserves the order of effects in video effect chains that were created in VEGAS Pro 15 or earlier which involve pre-Event Pan/Crop effects and post-composite track effects
• Manually adjusting the Zoom slider properly disables the Auto-zoom checkbox 
• Missing Aspect ratio options have been add back to the Properties dialog box
• The Use Current Project Folder option has been fixed in the Advanced Save utility
• Text boxes scroll correctly when Scroll inactive windows is enabled in Windows 10
• Render template Frame Rate settings properly use a period or comma based on the language the application has been installed in
• The Project Media window is no longer limited to showing just 100 thumbnails
• Project Media thumbnails do not redraw when there are more than 49 shown and you move the mouse over them
• Improved thumbnail reading in the Project Media window avoids crashing
• Variable frame rate media plays back with properly synchronized audio
• Fixed issue where improper thumbnail can appear for generated media in the Project Media window
• Fixed issue where some MP4 files crashed the application when loaded into VEGAS
• Audio Event FX window no longer remains open after deleting the track from which the audio effect is applied to
• Issue when envelopes move in the wrong direction when using the CTRL key while dragging is fixed
• Fixed crash when loading some plugins on startup

Notes

• Checkerboard artifacts may be visible in HDR external preview when preview quality is set to "Best" with certain kinds of footage; please switch to "Good" quality in such scenarios; this does not affect the actual rendered output
• Very bright yellows can blow out with the default ACES Rec.2020/1000 nits IDT; please use Levels FX to adjust the footage to work around that.

Is all NLEs like this, i.e. only CPU decoding of video on the NLE timeline?

Resolve is considered best with their latest update. But you need Studio version for this to work.

When I play back a 4K clip from the SSD or from YouTube it's full GPU video decoding. So a bit surprised that this is not done in the GPU also within the NLE!

It is because developers required or this to work really good are of different qualification compared to most other ordinary guys. And non leading companies frequently can't even get such people as can't compete for them due to money shortage.

New build 361 available now at: http://rdir.magix.net/?page=TXCZ0TBOYSA9

Bug fixes

• Crash that can happen when OpenColorIO library is not installed properly is now prevented
• Incorrect values in metadata for HDR renders has been corrected
• Improved handling of hardware dependent video plugins when GPU does not initialize properly
• Likelihood of crash when resizing thumbnails in Project Media window has been reduced
• Improved performance of thumbnail drawing within the project media window
• Problem with some valid video plugins not appearing in the plugin chooser has been resolved
• Crash when launching on a 2 GPU system when with one GPU disabled has been fixed
• Smoothing parameter is now available in the basic mode of the Video Stabilization plugin
• Crash when updating a grouped track that is not visible has been fixed
• Crash when reading certain MP4 files is now prevented
• Disabled some JDR project properties for non-HDR projects
• Disabled HDR preview preference for 8 bit projects
• Crash that may occur if the timeline ruler and speed controls are not visible as been resolved
• Crash they may occur when beginning a render of building peaks or other similar tasks has been resolved

Some truth about Vegas (in Russian)

Yet considering Gary being Product Owner, it is just such title in Magix, nothing more. They have same titles (and same total mess) for their own old titles.

@EspenB

May be $1000? :-) Looking at their progress.

From their forum post

We've made comprehensive workflow improvements, such as Nested Timelines that provide the power to better organize complex and long-form projects. The new Color Grading panel streamlines the workflow in a quick, efficient and logical process. Another highlight of the new version is the optical-flow slow motion for incredibly smooth slow motion. Optical flow technology that analyzes one frame to the next and then creates intermediary frames between them.

If you crave more details, here you can see all new features:

• Nested Timelines This is a further development of the existing nested projects functionality. Where a nested project has to be opened in a second instance of VEGAS Pro for editing, with the nested timelines it is now possible to create and edit a "project-inside-a project" directly from the timeline.
• Color Grading window: Several color-related Video Event FX (including Input LUT, Color Wheels, Color Curves,HSL, White Balance and many more) are combined in a dedicated screen area that is easily shown or hidden with a toolbar button. To save you a lot of clicks it can stay open to apply the desired color grading to the different events, instead of opening each event's FX chain and loading the color FX separately.
• LUT Export: Save all color effects from an effect chain as a CUBE file with the Save LUT button in the Plug-in chooser window.
• Improved Storyboard functionality: You can add the same piece of media to a single storyboard, and thumbnails reflect the in point of the media that is used in the timeline.
• Warp Flow transition/Smart Split: The Warp Flow transition automatically fixes jump cuts by synthesizing movement. The Smart Split command cuts out parts of an event and applies the Warp Flow transition to conceal the cut.
• Mesh Warp plug-in for creative deformation of your footage, or, when you set the grid size to 1x1 it gives you four corner points to quickly conform your video to a non-rectangular four-sided surface.
• Lens Correction plug-in to compensate distortions from wide-angle lens systems as used in action cams.
• HDR Color support enhancements
• GPU-based processing
• Windowed HDR Preview (preview in the Video Preview window)
• HDR Specific color grading
• HLG support
• Stabilization improvements: Using the Video stabilization is now also possible at event level, when used on event level it is possible to visualize the motion tracks of the stabilization.
• Collaboration Center: Attach notes to your project if you want to hand it to someone else. The notes can be tagged as "resolved", resolved notes can be hidden.
• Automatic Slideshow Creator: Create a Slideshow of a desired length from a folder or selection of pictures.
• Adjustable Color temperature enhancement to White Balance plug-in.
• Audio synchronization for multicam: Synchronize Multicam footage by analyzing and matching the audio track of the recordings.
• 8k support : You can add 8k to your project now when using proxy files.
• New Formats:
  • Experimental MKV support.
  • 10 bit intermediate format
  • ProRes 4444 files with embedded alpha channels
  • NVENC 10-bit HEVC rendering
  • Hardware decoding for AVC and HEVC
• User Interface improvements:
  • You'll get a warning when you delete a track that has events on it.
  • Hi-DPI interface improvements: The High DPI mode is now defaulted to on for VEGAS Pro17
  • You can display the Event length on the header of timeline events. Find it in the hamburger menu for each event or under the View menu.
  • Temporarily ignore event grouping when moving an event: Hold both the left and right mouse buttons as you drag an event to move it independently from other group members.
  • There's a new indicator on an event to show if Media FX have been applied to the media the event holds (find it in the event hamburger menu)
  • You will be asked to confirm if you click cancel in a render process.
  • New, task specific, default layouts / Dashboard:Easy editing modes for beginners work with a simplified version of the user interface that show only the most important controls for a step-by-step walk-through from adding media to the final movie, everything put together in the Dashboard window. The Guided Video Creator from the Tool Menu takes you through these steps.
• VEGAS Screen Capture utility: Record video streams from your browser or video game.
• Motion tracking: Track motion in a scene and let other events or text follow the movement.
• Super-smooth slow motion (optical flow and motion estimation) with the VEGAS Slow Motion plug-in
• Bugfixes:
  • Render As dialog box shows the correct disk space when switching disks
  • PreRes files creating with the RED Epic Helium camera are now properly supported

Finally there are some GPU improvements.

VEGAS Pro 17 Update 1 with lot of bug fixed

New Features

• The Bézier tool's motion tracking has been upgraded to track perspective change allowing for more effective planar tracking
• Navigation to exact timeline markers through typing the marker number on the keyboard number row now supports three-digit marker numbers
• An option for opening a media file in VEGAS Post has been added to the event hamburger button
• The VEGAS Screen Capture utility now provides the ability to save a capture project file which can then be imported into VEGAS Pro so that all captured media is imported onto the timeline on separate tracks and synchronized for instant editing
• An extension has been added to automatically adjust the length of an event after applying a playback rate change with the Slow Motion OFX plug-in
• The Warp Flow transition has been optimized to provide interesting results with a wider variation between the video clips involved and more gracefully defaults to a crossfade in extreme cases where warp flow calculations cannot be made
• The Video Stabilizer now automatically determines and uses the most suitable reference frame for freeze motion mode
• Uploading to social media sites process now uses the efficient rendering of the MAGIX AVC/AAC file type for faster rendering and uploading process
• The PiP Copy script now supports copying tracked perspective motion from the Bézier tracking information to the PinP plug-in
• Menu options for opening a file in FXhome HitFilm have been consolidated for more understandable presentation
• Several improvements and refinements have been made to the Smart Split feature including the addition of a preference that enables the user to change the default transition length
• VEGAS Pro now supports NVENC-based lossless encoding templates on qualifying Nvidia hardware

Bug Fixes

• Unreasonably long load times for large projects with many events have been eliminated
• The splitter between the preview and audio waveforms in the Trimmer window has been restored so it is possible again to change the height of the audio waveform area.
• Stabilization crash on certain files eliminated
• Custom NVENC templates from earlier version of VEGAS Pro can now properly be used for render
• Text editor button icon display problem corrected
• Edge cropping of the Video Scopes window no longer occurs
• User is no longer prompted for new instance or clone when creating nested timeline with generated media
• Controls are no longer overlapped in the uploading to social media dialogs
• the Bézier Masking plug-in now correctly updates for shape and location changes
• Use GPU processing for ACES color management preference artifacts eliminated
• Color Grading Panel controls that could disappear under certain specific actions now properly remain
• Custom values entered for the Pixel Aspect Ratio media property media in the Media tab of the Media Properties dialog are no longer inadvertently erased and ignored
• Adjusting overlap time of the Warp Flow transition no longer causes the software to hang on playback
• Mouse clicks in the Project Media window list view now properly selects the clicked-upon media
• Smart Split procedure is now properly identified in the Undo drop-down list
• The Picture-in-picture script no longer produces an error if the user attempts to run it without first creating tracking information
• A crash upon opening VEGAS Pro after closing the application with a saved project has been eliminated
• You can now undo adding the Color Grading Panel plug-in to an event
• Replacing a Main Timeline storyboard item that is a duplicate no longer removes all items that reference the same media
• Slow motion artifacts when processing with the CPU have been eliminated
• Warp Flow transition now properly stores the necessary tracking data
• It's now possible to properly apply different edge filling across different events
• No longer crash upon attempting to load older, unsupported Boris Continuum plug-ins
• Creating a nested timeline no longer deletes markers or regions from the parent timeline
• Various translation problems have been fixed in different international versions
• Hover scrub no longer crashes or stops working after an undo/redo of a media replace or delete action
• A one-pixel "jump" between the stabilization freeze mode reference frame and the following frame has been eliminated
• Double-clicking a file in the Explorer now properly adds media to a selected unassociate storyboard
• Events are now placed in the proper order after adding duplicates to the Main Timeline storyboard
• The Picture in Picture plug-in now works properly during playback and render after copying motion tracking information to it
• No more green frames for 422 AVC MP4s during NVDEC hardware decoding
• Windowed HDR preview now properly updates during render
• ACES version and ACES color space properties changes no longer persist when user cancels changes in the Properties dialog box
• Image adjustments are now properly applied when Slow Motion is used as a video output effect
• A warning message is now properly presented when the user attempts to prerender a video without first choosing a render template
• Some render templates that showed the wrong vendor information have been corrected
• The X and Y Location sliders now properly adjust the location values when animating location settings for various plug-ins
• Several minor UI problems have been addressed
• The Color Grading panel is now properly disabled when more than one video event are selected
• Many corrections have been made to the application help
• Project Media context menu command Remove from Project now does what it's supposed to do
• Color Grading mode parameters are properly read when reopening the project
• Audio/Video synchronization problems that could occur in HDR projects have been resolved
• Several Hi-DPI UI issues have been eliminated
• A problem that could cause a crash on playback or render in a project with Event Pan/Crop mask keyframes has been solved
• An issue that caused MP3 files not to play back on certain machines has been removed
• Hi-DPI preview no longer clips on a secondary monitor
• AVC playback on some machines that displayed poor performance have been improved
• Various improvements have been made which apply the new UI look to older components