http://www.videogamer.com/news/wii_u_gamepad_runs_3-5_hours_on_full_charge.html
This is basically the same amount of battery life as a handheld console.
The controller also takes 2.5 hours to recharge, and you can only recharge using the AC cord provided
(there is no usb recharge):
http://www.wired.com/gamelife/2012/09/trinen/
If you're planning on doing any gaming for extended periods of time, you better hope that there's an AC outlet near your chair/couch.
What do you think? Is 3-5 hours of battery life for a home console controller enough for you? Is no USB charging an issue?