I can kinda see the appeal, and it is a great tech showcase, but I think I'd get bored real quick and I'd be surprised if other people didn't (but then I haven't tried other pet games, so maybe this is a good implementation?). Specifically I look at things like the draw-a-toy demo that look cool, but every time the plane is summoned, the player grabs the controller and it spirals up into the air. That is' it! Once the novelty factor has worn off, what do the toys etc. offer by way of entertainment?
Aside from that, I presume the lighting will clash, messing up composition. Is there any calibration option to match the rendered graphics with the camera source? You could certainly get the white-balance. You could also create a hack ambient lighting texture by grabbing the background scene