Hmmm... Upon closer inspection of Oculus Rift, I can only say that I think this is more than likely just a "working vacation" for Carmack.
Don't get me wrong, I support the idea and ideal offered by Oculus, but I can't really see anybody but the truly obsessed (or the military) with money burning a hole in their pocket to actually shell out for a $300 head mounted display especially in the current economy.
VR Devices not too different from Oculus have been built, marketed, and failed in the past. (VirtualBoy, Dactyl Attack, etc. If nothing else, they're gonna have to make it a lot cheaper, lighter, and less bulky to use. Those headbands WILL get sweaty and nasty with use.

)
Something that DOES have a lot of potental yet to be explored is the old lightgun concept that somebody around here recently played around with. (Used DP and a hacked together wii-controller in a airsoft frame I think?)