Check out Thom's review of both the 70-200 f2.8 and the 80-400 f4.5-5.6. He gives both good reviews but thinks that the 70-200 is one of Nikon's best lenses and prefers the 70-200 +2x tc combo to the 80-400.
I'm considering the same dilema myself once I get the funds. I think from all the excellent reviews of the 70-200 that it is the way to go. This lens seems to have everything all rolled into one.
Like others I went for the 70-200 f2.8 VR +1.7x tele. Superb combination AF and superior to 80-400 zoom (which by the way can not use Nikon teleconverters).
If you need something longer go Nikon zoom 200-400 f/4 (can use the 1.7x tele, expensive $5000 bucks) or go with the new 300 f2.8 VR (expensive too). You can get a 300 f2.8 no VR version in KEH for a good price. Tripod a must with these lengths.
I handled a 80-400 and the AF is slow, slow, nothing compared with the 70-200 even with the tele 1.7x. <_<