The ability to position and manipulate virtual objects "in" the physical world. It's also supposed to be capable of 3d video playback and capture. 2d screens

The ability to position and manipulate virtual objects "in" the physical world. It's also supposed to be capable of 3d video playback and capture. 2d screens can't really do 3d, and definitely can't put things in the room around you. People have already dreamed up all sorts of game ideas for passthrough AR, as well as CAD and 3d design (think autocad, blender etc.). If you're using it as a stand in for a 2d display it may not be worth it -- it's just bigger in your field vision.