800mm f/5.6...lighter than 600mm f/4....nice!

I'm not saying an 800 isn't useful, but I'm finding I prefer a 500+TC over an 800 -- the 500 is lighter, shorter, wider FOV and shorter MFD. Right now if Nikon released a 7 lb 500VRIII w/pancake MTF like Canon's 500MKII, I that could be the last supertele I'd ever buy -- and that's shooting FX for the rest of my life.

Consider such a 500+TC14EII should yield 700mm of decently flat MTF at f5.6...only 100mm less that the 800VR...the 800 comes with a lot of extra "baggage" with not a lot of extra punch.

If you need the reach, get a V2.

Just my experience.

--
Gary -- Some Nikon stuff -- and a preference for wildlife in natural light
www.pbase.com/garyirwin
http://photographersonlinemagazine.blogspot.com