Just got off the phone with Canon Canada. They claim I need a "class 10" card.
Is that faster or slower than UDMA 7? She basically said 600x should be enough, speaking in those terms... I wish Canon would just say flat out, exactly what's needed on the website.
Class 10 would be the designation for an SD card to use in the camera; but if you're doing a bunch of burst shooting, you do not want that. You want a UDMA 7 CF card; the MkII only supports UHS-1 SD cards, which top out at something like 25 mb/s write speed. It takes a LOOONG time to write a burst of RAW to the SD card.