My battery life is also horrible. I leave home fully charged in the morning, and it's dead by noon. It shows 70-80% of the battery usage is from "Media", whatever that is. I used to make it through a whole day.
I should add a caveat-- many, many things aren't working for me in GB. The Music app hangs on startup (so does WinAmp and PowerAmp). I can't load any new apps from the Market. And just about every app seems to hang and force close now. I am clearly looking at having to do a factory reset but I'm waiting for a good way to backup app data before doing so. So my battery life issues might be related to GB or just because my phone is so messed up.