Depends on useage, I guess. Different apps will have different loads on the system. If you're playing a graphics rich game for a few hours, the battery will drain faster than if you're using a calculator.
Well, I haven't tested to simply get the battery life, but I last night I was listening to music, surfing the net, and playing games, and I still had at least half my battery after 2 hours or so.
Thank you guys. 3 or 4 hours of playing games, 2 hours of internet, games and music... that's really a big improvement. Though, for me personally, think i'm gonna order an external rechargable battery (not even enough for 1/5 of my flight)