The actual technology that makes it worth it is 3D. The screen size and features seem to be pretty much the same as the current DS. I don't really find the motion sensor on my iphone to be that 'fun'.
Because of the games... I'd be willing to dish out $200-$250.
I am a Gamer... I play games and not consoles. I have a PC and Console on which I game... I like games. End of Story!