Finally, Nikon has released a firmware update to address some minor issues. Some major features include 100% viewfinder in HDMI-out (up from 95%) in the D600, improved AF-C tracking performance for the D800, and support in both cameras for that new 800mm f/5.6 that I know you all ordered recently... Update: Even more DSLR firmware updates added from Nikon, too!
Below are quick clips of the performance improvements and bug fixes you'll see in the new firmware. One odd note is that there's a mention of Adobe RGB gamut tweaking on the monitor of the camera, citing an improvement in vivid picture display. However, there's no mention of whether or not this improves the actual accuracy of the colors (of course, it can't be perfect...).
While some updates are more major, others are simply for compatibility with Nikon's new 800mm f/5.6 lens. But Nikon will tell you what the changes are on the site when you download the update.
Want to check if there's an update for some other gear of yours? Check out the current versions here.
D600 firmware update changes/fixes:
D800/D800E firmware update changes/fixes: