I've also found that the device itself becomes uncomfortable after wearing it for a short period. I have however worn it for more than 2 hours in a row once or twice.
My niece (6 years) loved it so much she kept playing with it for hours also; She played Roboraid or just placed holograms in the living room like little dolls. Took me 10 minutes to clean up :-).
Not everybody I've had try it, were as impressed, and I think most people I've shown it to, think of it as a gimmick.
I don't think a lot of 'lenses will find their way under the Christmas tree this year. Too expensive. But if they got the price down around the cost of an iPad, it would blow the success of iPad away -- Even in the 'lense's current form...
It is another one of those things that indicate that Microsoft is on the right path as a tech company. Now, where is Apple's AR product?