According to Iwata, players will make a seperate usere account ID (I assume that's the nickname), used for save game settings, save data, pre-installed software and Wii U games to the console.The account will also allow users to save bookmark's for the console's internet browser and save play history. Some games will allow you to share save data among multiple users. This ID will be used when the console is first turned on, to select a user. With the Nintendo Network ID creation,(I assume it' a randomly generated #) you're asked to input a password, your date of birth, gender, location and e-mail address. It is used for Miiverse, eShop purchases, and video chat. You'll be able to register friends using this ID and determine which account on your Wii U as well as which account bough which downloadable games. DLC and downloadable games can be accessed from any other Wii U account registered to your console. Nintendo Network will also be compatible with different network services from other game developers. You'll use your Nintendo Network ID to sign on to each third-party network's service.
I don't think any other major details on Nintendo Network have been mentioned yet.
http://www.polygon.com/2012/11/7/3612606/what-to-expect-from-the-wii-us-nintendo-network-id