The Wii U uses a new account system for user accounts, Nintendo president, Satoru Iwata, shared in a Nintendo Direct presentation this morning. You can register up to 12 users per console and each one is represented by a Mii.
User accounts are used to separate custom game settings for individual pieces of software, Internet bookmarks, play history, as well as game save data. Some games, however, will allow you to share save data among multiple user accounts on the same console. The first thing you do when you boot up your Wii U is select the appropriate user account that you will be using.
User accounts are tied to consoles, however. To purchase games from the Nintendo eShop, use Miiverse, or the video chat function, you will have to register a “Nintendo Network ID,” which will require you to input a password, gender, date of birth, e-mail, and area of residence. A single Nintendo Network ID can be used to download software and purchase add-on content, and this content will be available to all user accounts on the Wii U console in question.
Iwata also adds that the Nintendo Network will work with network services from other software developers. Once you link your Nintendo Network ID to other services, you can use it as an all-encompassing ID that lets you sign into each separate service.
Your Nintendo Network ID will also be available for use on Nintendo devices that are released in the future. Additionally, it will also be compatible with planned services that will be rolled out on PCs and smartphones, which will allow you to browse the Nintendo eShop and Miiverse without a Nintendo device.
You will also be able to transfer content from your Wii to your Wii U, Iwata confirmed. Both WiiWare and Virtual Console games will be transferrable and more details on this front will be announced later.
You can view the English-subtitled Nintendo Direct presentation here.