Because of the larger screen it does use a bit more battery than the original Droid in comparable use. However there are things you can do to increase your battery life. For instance turning the screen brightness down, turning off the GPS until you need it, and choosing to sync contacts, emails, and social networking less often.
The update that rolled out a couple of days ago has improved my battery life pretty good. I can get through 2 days of moderate usage without having to charge it. I'm sitting at 60% battery life right now and I haven't charged it since yesterday morning. Hopefully once Android OS 2.2 is rolled out it will increase the battery life even more. All in all the battery life is pretty decent for the size of the screen and the capabilities of the phone. You need to realize though that no smart phone on the market is going to have incredible battery life like a flip phone or just standard cell phone.