Long story:

Bought a Samsung SD 16gb Plus Class 10 (this kind: http://www.amazon.co.uk/Samsung-16GB-Class-Extreme-Speed/dp/B00569J5JC/ref=sr_1_5?ie=UTF8&qid=1327802435&sr=8-5)

First thing I did was format it at 32K and 64K clusters for optimal speed and benchmark it. Speed gains from 64K were marginal, and IIRC the camera didn't like them and defaulted to 32K if I formatted in camera.

Benchmarked the card at almost ~15MB with 16MB files and ~13MB with 8MB files. "Nice!" - I thought, 15MBs is better than Class 10 and since it's 120Mbps it will hold some pretty aggressive patches for a card that costs 20€.

But one day as I was moving FW from my laptop to the card I noticed the transfer speed was way below 10MBs! :( This started a heavy series of benchmarks that were all flawed (basically the problem was that the internal SD reader on the laptop is speed limited) but that had an unexpected development in my struggle to get the benchmark back to the speed I knew it was capable of. In that series of events I used some SSD reasoning "It's flash memory, I should try a Full Format not a Quick Format."

When I returned home and benchmarked the card on the external reader where I originally got almost 15MBs, this is what I got:

I don't know if this will transport to other brands, but I know I'll be doing this every now and then....