I just got my GH3 today, and of course the first thing I had to do was this test. I threw the GH1 in there out of curiosity since I had one lying around. It looks like the GH series hasn't had much progress in the highlights, but the shadow detail has gotten much better. The GH1 and GH2 were hacked while the GH3 was using the stock 50mbps IPB setting. I chose this over the Intra because of reports that it held up better due to a more efficient compression algorithm (I don't know though since I've only had the camera for a day).

I used the cameras' spot meters on the big square gray patch (which is supposedly 18% gray), but I think the GH1 was a little hotter than the other two cameras when correctly exposed. Base ISO was used on all three cameras to achieve maximum DR. In post, I raised or lowered each image by one stop increments with Colorista II to compensate for the increased or lowered exposure levels. Hope someone finds this as useful as I have!