I've been having reasonably good luck with the 32GB Transcend 1000x, was going to try out a KB card but the Transcend was on sale at B&H for $85 with a free reader so I went for it. The reader is the Transcend USB3 one, which is UDMA-7 compliant. So far I've been able to capture at 1728x972 (on a 7D, of course) continuously, with Global Draw off. The Warm Up card option seems to help as well. I hear a lot of debate about the KB vs the Lexars, but not many people talking about these cards. Probably because they're terrible and I've made a huge mistake, but I'll live with it.