Apple update iOS to iOS5.0.1. This new version iOS5 is updated for solving power leakage on iPhone 4S. There are customers complain about the battery life of recently released iPhone 4S.
There are some users found their battery can not meet their expectation when they turn to iOS 5. Just a 50% battery life will remain after 3 hours stand by. The battery on their iPhone 4S can not sustain one night.
Apple did research on this problem and confirmed the issue on 3, November. They said this problem is caused by a soft bug in iOS5 and promised to fix this bug in few days.