It seems the only way to preview RAW video is as B&W slow frame rate type - in essence it makes the preview unusable to judge if you got the shot or not (you can't judge the performances of actors or make time specific judgements). It would be great if we could great some kind of low res proxy that allowed one to pre-view the video in real time.
http://www.magiclantern.fm/forum/index.php?topic=5887.0
And discussed to death when raw preview was coded many months ago.