Been reading a lot about battery issues on the 3GS after you upgrade to 4.0. People seem to think the multitasking is causing the drain, or the wifi, or _____. I had lower then expected battery life when i did the upgrade. I decided to back up my data (pics, bookmarks, notes...etc) and restore the phone as "New". I DID NOT use a backup to restore the phone. Once the phone was setup as new I installed all my apps, and put my data back on it. I had to setup all my apps again, my e-mail, and everything else i had customized. this was a pain in the ass and took a lot of time however i have gained over 2 hours of battery life. Maybe when you just upgrade 3.x to 4.0 you can get a glitch. Like trying to upgrade windows.....its always better to do a clean install over a upgrade. I have every feature turned on....(push, wifi, location service...etc) So with 2% of my battery left i have: Usage: 5 hours 15 minutes Standby 1 Day 1 Hour. So if you are having battery issues try to set your phone up as "New". Do not restore from a backup. hopefully this will help some people.