This seems to be hit or miss. I got two of Patriot LX 8GB class 10 cards, one is full size SDHC I bought several months ago from mwave, cheap with rebate + review coupon, the other one is micro SDHC bought on BF/Cyber Monday with the same price $5 after $5 rebate. Both cards write a lil faster than 10MB/s, but no more no worse. So they are exactly class 10. I'm using the full size card in my DSLR camera for photo and video and I haven't got any problem.
I got a PNY 8GB microSDHC class 4 which can write at 9.8 MB/s, so this can be a class 10 but may not be better than other class 4 though.
The reviews on newegg are mixed too, some got 4MB/s, some got 10MB/s, some DOA
As for the rebate, I got the first one, not so sure about the second one though