I really hope they get the accurate tracking and depth and getting objects to "stick" where they belong in 3d space correctly, without moving out of place or floating in a wrong way, with quick head movement. If they can do that, most of the battle is won and it will be amazing.

Edit: although, of course they'll need some intelligence on the surroundings to identify surfaces and stuff. But imagine like re-decorating your work room, adding scifi textures or something, and maybe pipes or whatever ;p