Well now that one of my 32GB SanDisk Extreme's has failed and there is apparently a lifetime warranty, but in the mean time, I need a few more SD cards, so the Sony UHS-1 at $19 for a 32GB looks like a pretty good deal and UHS-1 does seem like it is faster:
Re: SD Cards revisited UHS-1 v. Type 10: Micro Four Thirds Talk Forum: Digital Photography Review
I did a test last week when I received a Sandisk 32GB UHS-1 95MB/s SDHC card. I compared it with a Transcend 32GB Class 10 30MB/s SDHC card. I have just run the test again so I have repeatable numbers.
I set up my E-M5 for 9fps and held down the shutter until around 14 shots were fired and the buffer filled (RAW + LF JPEG). Then I timed how long it took for the card-writing indicator in the LCD to stop blinking. I did this a few times for each card.
I found that it took roughly 28 secs for the Class 10 card to clear the buffer, and about 11-12 seconds for the UHS-1 95MB/s card to clear the buffer. Additional runs seem to show this 2.4x speedup is consistent. I'm just counting ticks on a clock, so there's a small margin of error and these are ballpark figures, but it seems to be fairly repeatable.