That is a really good point. I seem to remember a really interesting article posted to HN awhile ago that went over all the pitfalls in depth. I'm really wishing I had bookmarked it now.

I think I'm going to have to rewatch the promo video in depth to see if they have any unrealistic demos with glasses-wearing users.

I still believe this technology would be really useful for doing Real Work. You could get around the shadow problem by working in a black surface. I am imagining an interface with a black drafting desk, small bluetooth keyboard, and a 3d tracked pen with this AR display could be absolutely revolutionary for certain engineering disciplines.