I was prepared and so it was no big deal. Bought the Wii U, brought it home and played it for a few hours BEFORE I connected it to the internet at all. Once I was ready, I connected to the internet, was prompted to update, then I went to bed and let it update all night.
In the morning, the update was complete. It can be a pain in the ass, but this story has gone mainstream and so I would hope most consumers would be smart enough to plan ahead. Also, the idiots that bricked their Wii U's should have read the giant message "DO NOT TURN OFF" while it was updating.