D4---why?

The D3 was an example of Nikon not following Canon. They built a fast full frame camera, something Canon didn't seem interested in until the 1DX which is still yet to be released. Prior to the 1DX and 5Dmk3, if you wanted a full frame sensor in a body that could fire faster than 3.9fps, you had to buy an $8000 1Ds mk3. If you wanted one that could shoot faster than 5fps – you were out of luck.

The D800 is a clear response to the 5Dmk2 and as I said earlier, is the camera many expected from Canon, not Nikon. The difference with the D800 is it's a huge leap forward.

Lastly, I do think in all these discussions some people need to maintain a sense of perspective: the reality is we've never had it so good.

Five years ago, there was no full frame Nikon DSLR. Their CCD sensor cameras were no match for the Canons in low light. Since then Nikon has released six full frame CMOS sensor cameras, with a 7th one (D600) rumored for release later this year.