A firmware update appears to have finally become available for the Wii U, a little later than Nintendo personnel had predicted. Pre-release Wii U systems are now able to at least begin downloading the update. I'm trying to download it right now and will let you all know how it goes and what features become available.
Without the firmware update, Wii U systems have been unable to go online, connect to Nintendo's Miiverse, or even play Wii games and transfer data from Wii games. That functionality should be included in this update. I'll keep you posted.
The system launches in five hours.
UPDATE: It's one hour later and the download's progress bar is up to the "g" in "Downloading data for update..." Potential Wii U owners might want to plan accordingly. The system can't be used during the firmware download.