I think the reason may be I haven't completely charged it because it was stuck at 99% for like an hour before I took it off the charger. I finally just let it charge all night and I will see how it goes today. I'm curious to see how everyone else is doing with battery life.
Also, if you could, state which ROM you're using and possibly what things you turn on/off to help/hinder battery life.
I'm running BAMF v1.1.1, my screen's on auto-brightness, I only sync my gmail account and weather, 90% of the time I use Wi-Fi, no GPS or BT on at all. I also have Juice defender on as well.
Edit: Well actually I just checked my phone and after about an hour and 50 minutes, my phone was down to 91%. about an hour and a half of that was streaming pandora on wi-fi. Maybe I just never had it charged completely. Screen on time was only about 20 minutes, though. I think that's pretty solid battery life. I guess I'll see how today rolls out.
Oh and also if you could state which battery you're using. I have the 3.7 V.
Edit: Since making this thread, my battery life has gotten considerably better. It idles just fine, now. I think there might have been something wrong with the screen off profile which was causing my battery life to be so horrible.
I would suggest using Scott's CleanWipe 5x when switch ROM's. I don't know why and it may seems a little unnecessary, but I'm getting a lot better battery life after using that and upgrading to BAMF v1.2 from CleanROM 4.1. Also, I turned off automatic brightness to 30% which I think has made a pretty good difference. The screen is a huge battery killer. I played Temple Run for like 20 minutes and the battery went down from 98%-77%. But I can get a 9% battery drop from sleeping for 9 hours with the phone completely idol.
It looks like 1/3 of the people are getting worse battery while 2/3 are getting the same or better. If I could revote I would and say my battery life is better now. So anyone hesitating to flash the new RUU. I'd say go for it. The odds are still with you: 66.666667% vs. 33.333333% that you will still get equal or better battery life.