Wii U users, there's a new firmware update available for your system. Clocking in at around 600MB, it doesn't appear to do anything drastic (like speed up loading and menu times). Here's what Nintendo says it does do:
Further improvements to overall system stability and other minor adjustments have been made to enhance the user experience.
UPDATE: Here's a friendly reminder from Nintendo
Wii U owners, please do not unplug your console while downloading updates. Doing so may cause damage to your Wii U.— Nintendo of America (@NintendoAmerica) December 5, 2012
Summary of System Software Versions [Nintendo]