Multiplayer/party games? That's pretty much the best part of the WiiU (or the Wii for that matter). Passing the controller for 5 hours isn't that hard if there are a bunch of people and the idea is to spend the night (we charged the controller when eating pizza :3).
My experience with the WiiU Gamepad is a bit mixed. It has great ways to add new gameplay elements (NintendoLand is a good example of multiple new ways of getting a multiplayer experience), but the problem is the limited battery life. I'd imagine the second revision of the Gamepad will fix this