Does MRAW not just resize the raw file? If it can downsample in camera that would be great.
Hmm it could definitely be great for video, but then stabilisation only works to a certain extent. The shortcomings of DSLR video are pretty much all still there and phase-detect AF isn't that big a deal to most people shooting video seriously.
Particularly with the 5D2 and 5D3 around, I'm not sure it'll catch on much with videographers, though the cost may have some role to play as if it presents a better video proposition than the Canon system and videographers used to using piddly (Super 35 or smaller) sensor camcorders are considering getting into DSLR/T video, not least as Sony has far greater market presence in video work than it does in stills stuff, or Canon does in video. (Yes the 5D2 is a video legend, but that was really by default as being the only 35mm 1080p-capable camera around, whereas Sony's position in the market has been fought for and earned)