I initially was very disappointed with the performance, my Sandisk 8GB 20MB / s was faster. But never mind, I decided to use it anyway. Soon enough, I had crashes loss of the card with pictures. Reformatting the card with the camera has not improved things.
So I returned to Amazon to exchange it for a Sandisk 16GB Extreme 45MB / s for little more expensive, and there, no problem, plus performance correlation with what is announced.
I suggest you avoid this product!