I just bought a Lexar 800x 64Gb CF card from Adorama and put it in my 5D Mark III. I haven't taken it out. I've been transferring via USB, then formatting the card in camera before I shoot again. Twice now, I've gotten corrupted files, and once a shot that I really wanted just disappeared as I was scrolling though the photos on the camera. This is the first Lexar CF I've ever bought. I've only shot with Sandisk up until now. I think I like Sandisk better.
5D Mark III, 7D, EF 24-105mm f/4L IS USM, EF 50mm f/1.4, EF 70-300mm IS USM, EF-S 17-55mm IS USM, Redrock shoulder rig, matte box & follow focus, Rode Videomic, Zoom R16, Sure PG42, DSTE Pro BG-E11, Excella Neo D400 Studio Strobes, Excella Stardust 50, 580 EX II, lots of other fun stu