well after having a great day out at the BTCC at Croft and the D800 working so well, ive gone and done what i thought i would never do, ive sold my D3.
The D800 just does everything so much better, the image quality is superb, the dynamic range is unbelievable with super clean shadow detail. Iso performance is at least as good as the D3 and because of the amount of detail retained at higher isos maybe even better. If you downsample the files to 12mpixel its iso is better than the D3. The Autofocus is quicker. Unlike the Nikon D700 / D3 where Nikon slowed the af of the d700 down even though it shared the same system as the D3, the D800 has exactly the same system as the new D4.
I would say that the D800′ s af system is faster than the d3 / d3s for initial lock on and accuracy abd then it just stays locked on.
Unless anyone wants the camera for sports, where the d4’s faster frame rate might help, the d800 is a better camera and only half the price which makes it a steal.
The slower frame rate of the D800 does not bother me and quite frankly with the MB-D12 grip, in DX mode its gets to 6fps anyway. I had my D3 dialed back to 5 because anything higher just produced too many shots to delete later.
The Nikon D800 is, in my opinion, the best camera that Nikon have made to date.