We didn't have the time or the resources (like multiple users) to put the Pre through the kind of lengthy, hard-hitting, take-no-prisoners battery testing some of you might want, but we did have a chance to use this as we would our own device for a pretty good run of days (we'll likely do a follow-up post with harder numbers for specific tasks, like media playback).
In terms of real-world use, the Pre battery situation is good, not great -- though we think that you can (mostly) put your Apple-inspired fear of background processes to bed.
During heavy use -- phone on all the time, browser testing, media playing, lots of conversations -- we could make it about three quarters of the way through a day without having to plug in. We weren't over the moon with how quickly we noticed the numbers dipping, but we also weren't completely surprised. Compared with the G1 (and we're talking 1.5 here), we'd say the Pre does a tiny bit better (or very close) on battery life -- but if you're a heavy talker or plan on running media on this all day long, you'll be reaching for the charger (or second battery) come dinnertime.
Still, for the battery size (1150 mAh) and amount of data being pushed, it didn't seem like the phone was performing unreasonably, and we don't knock the fact that you can snag a second (or third!) battery if you know you're going to push it. During the more conservative days -- which we think reflect the kind of moderate use we put our phones through -- battery life declined much less noticeably from morning till night. We'll be keeping our eyes peeled for third-party options with more juice, but the brick in the box isn't too shabby at all, especially given our expectations.