I see there is talk about Natal could potentially give boost to 360 sales. Based on videos it seems like a great idea.
I just can't imagine people are going to actually have a Natal unless its dirt cheap or it comes bundled with the console. It seems like a device that will appeal to casual gamers so bundling makes sense. Its basically just a camera so its probably cheap to manufacture. Also MS needs to include some sort of mini games like WiiSports.
Otherwise, I don't see the Natal having much of an impact. And if its about $100 it'll definitely fail.