The D800, a case for the higher resolution

Totally agree - and don't forget will also do 6fps in DX mode with grip attached. Also, does 5x4 format if you want (not many people seem to mention that on these forums but is potentially very useful in some scenarios).

For wildlife/birding etc I find that the AF is so good that I often get "the shot" immediately.  I tend to use the so-called "quiet" mode, the opposite of the machine-gunning approach.

For action (such as BIF in my case) the extra viewfinder coverage is enormously helpful (over a DX camera).   I am amazed at the camera's capability with BIF shots with my 300 F4 AFS (with or without 1.4 or 1.7 TCs) - it nails virtually every shot, even really cryptically camouflaged, fast moving small birds.

The only things I would wish for would be:  an actually properly quiet "quiet" mode and better battery life (D7000 does both of those much better).

Frank