Huge risk. Sometimes works, sometimes not, and sometimes fails at various times, e.g. removal, errors, etc. I am going with Sandisk Class 4 because they are very high quality and fast. I took my gamble on ebay, which I do not recommend if you need 1st-time-success. There are lots of fakes and you have to actually copy up to 20-30GB onto them to verify they are real.
Sandisk class 4 are one of the best quality. You can not (usually) buy this Sandisk class 4 on newegg, but they sell at Verizon, ATT, etc cell phone stores for outrageous prices. Surely this is because customers will return their phone if it fails.
Good luck.