People lose interest incredibally quickly. By the time the thing launches, all of these casual people who think its amazing will most likely say something along the lines of:
"Oh yeah, that camera thing by Microsoft. I wonder what John and Kate's Marital counselor is going to say tonight"
If NATAL was capable of the things that the demo video showed, then the "Vision" disclaimer would not have been pressent.
Periferals in general are not console sellers. MS SHOULD have held back with this and launched it with their next console. They should have learned from this generation that previous generations mean nothing for future sales. The could have bundled it with the console, then no one would care baout BC of games.
This was a big ball drop in my opinion, and MS really jumped the gun.