No idea what class it is. But generally speaking lower classes work better in mobile devices anyway. I suspect it's class 2. It was posted at £54.99 a little while ago.
Class 10 cards are optimised for long sequential reads or writes, not for the more random reads and writes that are typical for a Smartphone.
HD Video recording for instance only requires a Class 4 or Class 6 card.
I'm getting one for my Galaxy S2. Presumably HD video cab be recorded to the 16GB internal memory so no HD video issues there I suspect.