Updated to IOS 5.0.1 and "so far" it looks like my battery drain is worse. My 4S didn't have the huge drain like others, but was not real good. Now after the upgrade, it looks like the battery drain is worse. Sitting on my desk - un used, battery went from 30% to 26% in about 2.5 hours. Before update, it could last 4 hours before any drop at all. UPDATE took iPhone to genius bar. They said battery was ok, but useage and standby times we not good, so they gave me a new phone. The new one has IOS 5, I don't plan to update again until they sort out the issues.