Tee00 -- I'm pretty new here as well, but got my Eris first week Dec and worked with all the battery tips for 1.5. There are also battery considerations when going to 2.1, but if managed, better. I hope you're asking about 2.1, as that's the purpose of the thread. Look in the Eris Tips and Tricks thread if not.
When I first installed 2.1, without a factory reset or *228, it ate battery life like mad -- the first few hours after install, it got down to 40% without doing a thing but rearranging my homepage and a little non-streaming surfing.
Remained bad until I reset the phone (essentially making it a blank of the latest 1.5 build), programmed it with *228 opt 1, reinstalled the PB zip, then *228 opt 2. After that, initially thirsty... but both bars and battery life over a day got much better, never below 40% over an entire 12 - 14 hr day. I suppose it has a lot to do with what apps you have loaded and use, but I vote that 2.1 is more efficient with battery than 1.5
if you install properly.
