The excellent folks over at Lifehacker have a tip that seemingly works to resolve iPhone 4S and iOS 5 battery level issues.
The culprit? It looks to be a bug in the Time Zone settings that causes location services to go nuts and poll way more often than it needs to, draining the battery.
To remedy the issue, according to Lifehacker:
The solution for now seems to be manually switching off the automatic time zone updates located at Settings → Location Services -> scroll to bottom to System Services → Setting Time Zone. Expect more conclusive results in the coming weeks.
I’ve tried it and saw an immediate and striking difference in battery life. Give it a shot if you haven’t yet. And if you’re jet-setting anytime soon, just re-enable it (or take me with you and I’ll do it for you!)