It's quite interesting to view the results of a CNET poll on the issue, which are generally rather positive. The results show that 35 percent of Apple fans think iOS 5.1 has improved the aforementioned battery life issues, with 18 percent claiming the issue has worsened and 23 percent seeing no difference (the remaining percentage haven't yet updated to iOS 5.1).
If you're adamant the battery life of your iPhone 4S is seriously below par, it might be worth making a note of how you're using the iPhone and how long it lasts for without a re-charge. Then, if you're still concerned with the results take the handset to an Apple Store, and see if they can offer any help.
There are a number of ways you can prolong your iPhone's battery life, and we have a list of 10 in this article. The number one quick-fix, back when news of iOS 5.1's battery issues hit the Web, was to switch off location services for iOS apps which don't need to be aware of your location. I would also keep Bluetooth off if you don't use it regularly, and remember to have the handset auto-lock after a reasonable amount of time. A good starting-point, however, is restoring your iPhone in iTunes - for many, this solved any battery life issues they'd encountered. Just don't do this if your handset is jailbroken, because it'll update to iOS 5.1 (unless you've saved your SHSH blobs) and you'll lose your untethered jailbreak!
Let us know in the comments how your handset's battery life is holding up under iOS 5.1.