I'm getting fairly good battery life after all the mods I've installed. The rom I'm running tries to maximize battery life by having only essential apps running when not in use and I close everything after I'm done. I would estimate 7-8 maybe more hours of heavy usage and I estimate 3-4 days of standby(haven't actually tested how long). It's actually not the display that uses the most power but the OS lol. I actually just installed an over/underclocking app so my battery life should go much higher. With the underclock on standby it should last about 8 days I was reading XDA forums and several people have gotten about 40 hours of moderate usage on a charge, some people underclock and underpower the phone when not in use which extends the life a lot, here's a thread where people talk about how their batteries last.
http://forum.xda-developers.com/showthread.php?t=730978 edit: 8-2-10 decided to switch back to froyo now that it has been officially released and people are cooking stable ROMs, also decided to go with a new homescreen i've been getting much better battery life with froyo and i'm at ~40 mflops on linpack and before on eclair i was at ~7 so it's way faster now

damn it's a ton of fun customizing the home screen, here's another
