Nintendo also confirmed that you can use the GamePad as the main display for games, for when the TV is being used by someone else. they used the Wii Balance Board as an example and said causal games may use this. this could be that hardcore games push the Wii U more so it can't output to the GamePad, but that is pure speculation.
Nintendo also introduced Miiverse. this picture actually shows the start up screen for the console. you have the choice of using the GamePad to show the traditional tiles, which is default, or use the main TV and have this Miiverse screen on the GamePad. Miiverse is incorporated into every game and into many parts of the system. you can use it to send messages to other people, you can use it in game when your stuck to ask others playing the game for suggestions. Nintendo even shows a Demon's Souls style use where people can leave messages in the Miiverse at certain points in the game for others to see. an example was when you died, others who died at this point had written some comments, or when your on a map you can see other comments.Nintendo say the Miiverse is browser based so they can bring it to other platforms, to make it into more of a social network i suppose. they said it's coming to the 3DS, but it wasn't clear how many functions it would have, as well as mobile devices. however, it'll come to these other devices after the Wii U has launched.
other features revealed by Nintendo include the ability to use the Wii U GamePad as a camera for video calls, being able to take screenshots and sharing them on the Miiverse, being able to pause a game and use the Miiverse before coming back into the game, much like the PS Vita does, and being able to use the Miiverse to share user generated content.
this video has the full 30 minute presentation.
