I got here from FreshDV.
A fairly comprehensive real world review of the 3 big kahunas, including downloadable test footage. A quick summary:
-The D800 has the video resolution edge, but it’s not huge, and it’s accompanied by moire which is practically absent from the 5D.
-Some other reviews are saying that the D800 is as good as the D4 in low light, Dan says that’s not true, the D4 is better (but the 5D is better still IMHO)