Aside from all of the other points everyone has made, the D4 has an optional Wi-Fi tranciever that permits you to shoot tethered remote cameras which can automatically upload images as they are taken, to an FTP server. Also, I believe the D4 has the better video capabilities, but since I never use them, I can't really confirm my assumption here. There are also added controls on the D4 for vertical shooting, and backlit buttons; oh yeh, they have saved my bacon. Plus, it is a plus size DSLR. Meaning it fits great in plus sized hands, which I happen to have (4X Large). I've owned the D300, D700, D7000, D3 and now the D4. My favorite cameras have been the D3 and D4 because of an indescribable great feeling with respect to the ergonomics; it just fits. The D300 and the D700 felt about the same to me in terms of control and layout, although the shutter in the D700 had that more resounding snap (probably the larger mirror). The D700 is a fantastic sports camera once you add the vertical grip.