He will be spending his time at Oculus 100%, which is good, because there's plenty of new ground to break and few are better qualified to drive the software side of things for a new graphics technology than Mr. Carmack.
I had access to a Rift DK for the better part of a month. For what amounts to a smartphone screen mounted inside ski goggles, I was thoroughly impressed and have no doubt that this device offers an early look at the future of hardcore gaming -- I suspect a similar device that allows you to insert your own smartphone in front of a set of lenses could be the eventual template for casual gaming as well.
Among the many tech demos available, I was most impressed with Lunar Lander on the Rift, which was worth hours of fun. The illusion that you are actually there, on the moon maneuvering this vehicle was only slightly diminished by the development kit's limitations:
* lack of positional head tracking -- up, down, left and right work fine, but you can't lean or move your head in any direction as it immediately breaks immersiveness (probably a major contributor to the early nausea that I and others have reported)
* awkwardness of the headset, input box & wires
* lack of congruent body avatar in virtually all demo software to date
* low resolution screen (half of a 1280x800 LCD panel for each eye) contributing to what's known as the screen door effect
* various unoptimized latencies (LCD refresh, video card output, head tracking, etc...)
* clunky lens adjustments
Over time, continued software and hardware development will mitigate or eliminate many of these problems. I'm looking forward to the 2014 consumer launch which is rumored to have higher resolution and positional tracking. If so, I will definitely be one of the first to line up for it.