first of all on the back of the new version of the controller that are now more bumped our ridges on the side so it feels more like a regular controller, that little box right below the D pad is a item scanner (puts shit into your game, think skylanders), and the analog sticks also act as an L3 and R3. The tablet is also a universal remote for ANY device (specifically TVs though) and can function Without the system being on.

WiiU account system and social networking thing:

Okay so this thing us actually pretty cool. The system can interact with all other Wii U's even in single player games. A  posting system lets you do what a posting system usually does. They showed a trailer thing where a guy was all "hkabfhkbfhkasf can't beat this enemy" and ask for help on the nintendo network, got called up by some people on a video chat, and they helped him beat the enemy. Seemless flow from game to chat, and it does as the 3DS does by suspending the game for you, when it pulls this stuff up. You can also see little miis with qoutes above their heads of peoples status and comments about whatever level they're on. This Nintendo Network internet socializing account thing also syncs up with other devices, like phones computers etc.

Kick ass controller for those who don't want to use wii remotes or tablet:

So yes this thing controls the system as well and you can use it instead of the tablet if you want it to. It looks *crag*ing sexy. GUGHHHH SYMMETRY IN A CONTROLLER FINALLY GUGHHHHHHHHHH

There was tons of other stuff as well but this is the cool stuff.