When I bought my Wii, I was under the impression that it would be, oh I don't know.... accurate with it's motion controls? But it's not, it's like trying to paint with a mop. And after the pretty decent controls that Wii sports does have, all the other Wii games have been fairly lacking in either technology or creativity. What I mean is that most games have been reduced to waggle as a form of control. Even good games like Super Mario Galaxy, besides the star collection there's nothing in that game that couldn't have been done with a gamecube controller.
So in my opinion, accuracy and creativity will be the litmus test for Natal. If it can't detect subtle motions, or developers are unable to come up with interesting ways to use Natal, it's bound to fail. I'm still curious how they're going to implement Natal with things that require character movement, like an FPS without having any tactile controller.
