It take hours to complete
When you connect your Wii U for the first time it will ask you to install a 5GB firmware update.
The awaited Wii U was released yesterday in the US and it arrived without Miiverse, eShop, Internet Browser and backwards compatibility, so users had to wait for a 5GB firmware update!! Depending on your Internet connection, this update could take around 1 - 3 hours to complete, or even more.
Also you should be careful, as if you unplug your Wii U while updating you could brick your new system, like that happened to a few people already.
NEWS SOURCE: Wii-U's first firmware update is huge and takes took over an hour to update (via) SiliconEra
Our thanks to 'Robe24' for this news item!