Nikon's two new cameras, the $5,000 flagship D3 and its top compact camera the D300 ($1,800) look surprisingly similar on paper. Both have a 12MP sensor digitizing into 14-bits per channel; but while the D300 is the standard Nikon APS-C the D3 is Nikon's first full-frame camera ("FX" in Nikon's literature). Both cameras utilize Nikon's new Expeed chip fabricated by Fujitsu. The D3 can shoot at 9fps (the D300 is limited to 6fps) and has up to ISO 6400 calibrated (and 25600 pushed!)
In common, both cameras are environmentally sealed, both support an external GPS receiver, live-view, and 51-point autofocus systems. The D300 alone has an anti-dust filter. There is a lot less separating the two new Nikon than in Canon's equivalent line-up.