Nintendo doesn't have actual games to show yet, but there are a few interactive demos running. Chase Mii has Mario characters running around a maze and uses the Wii U controller's screen to track other players in the game. Battle Mii uses traditional Wii controllers as well as the Wii U controller, and GI says controls are a little tighter and quicker than the traditional Wii can handle (though the gyroscope in the new, presumably still a work in progress, controller is still a little awkward). Finally, Shield Pose has you moving the Wii controller around to try and block called shots coming in from a pirate ship, and is supposed to be fun in a sort of follow-the-leader way.
We'll look for all three demos on the show floor this week, so stay tuned for our own impressions on just what the Wii U can and can't do so far. There's not a lot of information available yet (the Wii U is due sometime in 2012, and there's no price listed at all), but already it looks like the Wii U will definitely shake up console gaming.
Update: The Guardian also got to play with the Wii U, and says the console will be HD via HDMI, and have internal Flash memory, along with SD and USB solutions for adding more. The system will be backwards-compatible with the Wii (which we heard at the press event), and play both discs and downloadable software.