I wonder if you'll be able to use these as an integrated solution for gaming (with the sound and microphone on). My guess is no, but it'd be nice to not have a wired connection with my wireless keyboard/mouse.
As a budding sports photographer who likes that 1.5x crop and is desperately needing to replace his archaic d80, I am looking WAY more forward to see what the d400 can bring to the table than the 800, whenever that may be. That being said, this thing looks like a pretty awesome successor to the d700.