What camera are you using it with ? I have used them completely successsfully with my Nikon D200 and my Canon 7D however there is a small problem when used in the 7D, you cannot shoot Full HD video with it (even with a Class 10 card) the transfer speed just doesn't cut it. Reducing the video resolution works but sort of defeats the purpose. If you don't shoot video then they work great. You may also get a reduced fps rate in continuous shooting mode with something like a 7D (8fps) but I never tested that.