On my Sony Xperia it lasts easily a week and I can even browse web on 3G (for example read the news), but if I watch YouTube videos and do heavy gaming on it such as San Andreas it doesn't even last a day.
That is generally background housekeeping (or NSA phoning home). I've take a few Android phones, rooted them, removed the phone-specific apps to make them dedicated portable media players. The resulting battery life was insane. Performance was terrific.Says "31% Phone Idle" - so got "Phone" in there somewhere