For one thing, the main controller is bigger. Now called the Wii U GamePad, the LCD touchscreen is still there, but the sliding circle pads have now been replaced by actual analog sticks. The most interesting addition for me was the Near Field Communication (NFC) sensor on the GamePad, which will allow the Wii U to communicate with a lot of NFC-enabled devices.
The Wii U also got an almost identical clone of the Xbox 360 controller, which they call the Wii U Pro Controller. But the best thing was that it also came in black, which I thought was more awesome-looking than the somewhat bland white version.
While they announced a lot of upcoming games for the console, including the prerequisite Mario titles, there were some surprises, like Mass Effect 3 and other games that were hits for the PS3 and Xbox 360. Now if they would only port Fallout 3; having an always-on Pip-Boy 3000 displayed on the GamePad would make be buy this console on the first day of release, heh.