Just wondering for those of you who shoot a lot of video; Is continuous auto focus (D800 has it, 5DmkIII does not) a good feature?
It's not enough for the body to have continuous AF. It's the body/lens combo.
What I found when I was looking into this is that DSLRs don't autofocus very well in video mode. Maybe the D800 is better, but I saw youtube videos of the Nikon APS-C cameras and their continuous autofocus behaved in a manner pretty similar to how the 5D Mark II would if you were to pound on the "autofocus" button in video mode.
That is, when it focus, the lens lurches and hunts, it doesn't glide smoothly like a camcorder or for that matter, a manual focus pull.
I have a Panasonic GF2 which seems to autofocus much more smoothly in video mode than any SLR. If video is important to you, and AF in video is also important I'd suggest taking a serious look at either a panasonic GH2 or a camcorder.
SLRs are fine for video, but the AF in video mode isn't really usable (at least none of the ones I've seen are) -- you need to be willing to manually focus.