I would like to go back to 2.1 as well. I am not rooted and I have 2.2, but for whatever reason, the battery life on the leaked 2.2 is terrible on my phone. With normal use on 2.1, I would go well over 12 hours and have 50 or 60% battery left, but with 2.2 I'm lucky I get 4 hours with light to normal use.
You must have something running the background like updates or wx checks,
delete the programs you added one at a time or check the battery resource .
There are utilities that shows whats running and how long.
such as "SystemPanel"
Thats the thing, Iv changed nothing since the 2.2 update. My screen brightness is all the way down, and my display is still #1 on my battery list (as it should be). I must say though, every since the 2.2 update the screen does look brighter and more vibrant, so maybe the setting for the lightest brightness is higher in 2.2? I dont know, all I know is that its because of 2.2 that my battery is much worse. It was so god after reading the battery thread, but now its awful again.