I've had my Palm Pre for over a month now and used it every day. And not once have I made it through an entire day without running the battery down to the 20% warning level. For a while, I didn't realize that the GPS is quite draining to have on all the time. Lately, I've had that turned off. I spend quite a bit of time in front of my computer and that is an area of weak cell service, so maybe that accounts for some of the drain -- the constant straining of the radio to reach a cell tower. Another factor may be that I constantly run the Classic emulator to manage my Tasks list, transferred from my Treo. It does background checking to sound alarms, which might be hard on the battery, too.
The good news part is that the battery recharges pretty quickly. Tonight, it chimed for juice at 5:40, so I put it on the Touchstone charger during supper, and when I checked back 35 minutes later, at 6:15. it was already up to 90%.