In addition to the announcement of the D700, Nikon has revised the firmware of the D3 and D300. The latest D3 firmware adds new function button customization options though not the ones featured on the D700. In addition to these and a virtual horizon in live view mode, Nikon has also addressed the problem that some users experienced in which the battery indicator would incorrectly register an empty battery.
This problem, which has come to be known as 'Dead Battery Syndrome,' has also been addressed in new firmware for the D300.

D3 firmware makes improvements to AF and Auto White Balance mode, as well as correcting for the battery indicator errors. Many of the other changes are subtle tweaks to menus and behavior, such as the decision to only all auto-rotate of images in playback mode, not in the review image that appears after shooting (as the camera must already be in the correct orientation to have taken the shot).

The only D700 feature to appear is the addition of a visualization of the virtual horizon function to live view mode. Other than this, the new function button customization options are not as extensive as its new baby brother. The D3 changes add three more options that can be assigned to the Function, Preview or AE-L/AF-L buttons. The only completely original option is the ability to scroll between shooting menu banks (user-defined presets) with a button press and turn of the control dial. The firmware also separates the image area (FX/DX/5:4) option into two, so that you can choose to either scroll between all three image sizes or just between FX and DX.

D3 firmware v2.00 can be downloaded from the following links:
Mac
PC

D300 firmware v1.03 can be downloaded from the following links:
Mac
PC

More details about the D3 changes can be found by clicking here.