Thanks Brian. As I say, having an FX D700, but no DX lenses I can't comment constructively. In the end I am now of the mind that I should forget the D800 for distant wildlife and wait and hope the d300s replacement (whenever) offers me 6-8 fps and high ISO, lower noise capabilties. Although APS-C sensor + low noise may be an athama compared to a FX sensor as proved by my D7000.
As an aside, yesterday I conducted some fairly tight printed target tests with my D700 with a 300mm f4 tripod mounted at ISO1000 on FX mode and cropped in Photoshop to DX size, D700 in DX mode and DX mode with a x1.4TC. I know this is hardly apples for apples and certainly not very scientific, when comparing what may be achieved with the D800 all things being equal. Interestingly, I saw no difference whatsoever in IQ between cropped, DX mode or DX + x1.4 TC. All cropped and DX images at 1/1000 @ f8 were very sharp.