Version 3.0.0-U/E (25 April 2013)
- New Features:
- A standby function to download and install software while the system is powered off
- Software purchased from the Nintendo eShop will automatically install in the background once the download is complete
- Holding down the B Button while the Wii U logo is displayed during startup will load the Wii Menu* 
- Changes to System Settings:
- An option to transfer and/or copy between two USB storage devices in "Data Management"
- The ability to select multiple software titles when transferring, copying, or deleting data in "Data Management"
- The option to adjust screen size is now available under "TV"* 
- "Auto Power-Down" has been renamed "Power Settings"
- Changes to Miiverse
- Changes to Nintendo eShop
- Changes to the Internet Browser
- Changes to Download Management
- Further improvements to overall system stability and other minor adjustments have been made to enhance the user experience
1 User selection may be necessary.
2 A similar option has been removed from Nintendo eShop, Miiverse, and the Internet Browser.
Version 2.1.3-U/E (5 March 2013)
- Further improvements to overall system stability have been made.
- The previously announced system update, which adds new features and further improvements to the user experience, will be released in April.
Version 2.1.0-U/E (5 December 2012)
- Further improvements to overall system stability and other minor adjustments have been made to enhance the user experience.
Version 2.0.0-U/E (19 November 2012)
- Added new Network features
1 In order to use those features, you will need to register Nintendo Network ID.
2 You can use this feature in Wii Menu.
3 Update feature is available only for the software which has update data.
Europe Launch System Software
US Launch System Software
Note: changelog taken from Nintendo