So I actually found a Wii U demo kiosk yesterday. After specifically trying to find such things around the Cube and Wii launch it's funny that I just stumbled across a Wii U demo without planning on it. I don't know why Rayman instead of a, you know, Nintendo game is being demoed but I'm sure that's been talked about.
For me the important thing was seeing how the Gamepad felt in my hands and what it was like to play a game with it. It feels good. It isn't unwieldy or heavy or anything like that. I was easily able to pick up Rayman and just play it. Though I didn't get asked to do any waggle or use the touchscreen (I only played one level; maybe the others ask that of you) so I didn't get the try the stuff that makes me iffy about the controller. Still, it so far has the ergonomics right so I'm happy about that. I know people have stated that already but it's really something one has to try for themselves.