After updating my AT&T iPhone 4 to iOS 5, my battery life dropped dramatically. Under iOS 4 my battery would be in the 70 - 80% range after a full day of use. After installing iOS 5 my battery was under 50% after about 5 hours and was under 20% after 8 hours. Turning off location services did not help. My original iOS 5 install was followed up by a restore of my iOS4 settings, which were probably restored from an iOS 3 install. I finally restored iOS5 and did NOT restore from a backup and instead manually installed all apps. After doing this my battery life is back to normal, if not better. I have push email and location services turned on. My battery showed 100% after nearly 3 hours. I don't know if it was a bad app or remnants from the old iOS backup that caused my battery drain. Whatever the case my battery life is much better now. Hope this helps others solve this problem.