3D UIs are a _disincentive_ to me. I don't have stereoscopic vision, and things that try to force stereoscopic images (3d movies, those pictures that are a bunch of random dots, etc.) all give me headaches if I try to use them.

Any "3D interface" (actual, not just things that have a 3D look) has to be something I can turn off, or I wont buy it. 3D TV's? Not interested. 3D computer displays? Not interested. Actively, decisively, not interested.