Originally Posted by Spin This!
Definitely depends on how strong your cell phone reception is as well too... if you don't get good reception, the phone work harder pulling down a signal. And that's cyclical: when you have low battery you'll notice you don't get as good reception as well...
This is probably the most import thing to consider when determining battery life. At my office I get crap for a signal so the phone is always trying to connect to at&t and the battery will barley last 6 hours. However at my home where I have a very strong signal the battery life is better then any smartphone I have had, well except maybe for my blackberry.