You know that warning that usually appears on your console when updating? The one that says "don't unplug while updating".
Don't do it; ever.
Especially on your brand new Wii U. LA Times film and videogame industry journalist Ben Fritz reports via twitter that unplugging your Wii U during the update will brick your console and make you extremely upset. How did Fritz discover this? Well, he did it himself.
Fritz disconnected the power cable from his Wii U 15 minutes into the update when it said it would take up to two hours.
Other gamers have shared their tragic Wii U tragedies via twitter as well. For one unlucky fan, the the connection timed out during the update. With an update that goes up to two hours, the likeliness of that happening is significantly greater. What's even worse than that is Nintendo's support supposedly told someone to unplug their Wii U for 15 seconds. Now they both have expensive paperweights.