A number of Nintendo communities are reporting that you can download the ridiculously slow Wii U update in the background. When the console asks you if you want to update the firmware, don’t do it. Instead, just click cancel. The update will then download in the background. if you’re prompted again, it should be saved in your system.
http://mynintendonews.com/2012/11/20/sounds-like-you-can-download-wii-u-firmware-update-in-the-background/?utm_source=dlvr.it&utm_medium=twitter
Nintendo and PC gamer