It seems that there are some issues with Apple’s iOS 6 as there are user reports indicating that iPhone 4 and iPhone 4S have battery drain problems after updating their iPhone’s to iOS6. According to Mac Observer, users iPhone’s drain more power when their devices run iOS 6. One of the users also reported that his iPhone 4S which was running on iOS 6 had 17 percent battery power by the end of the day, as opposed to 60 percent when the device was used with iOS 5.1.
This had also happen when iOS 5 released and users started reporting battery drain with iOS 5 installed. Guess will have to wait for this problem to get rectified when Apple releases the next update for iOS 6.