European carrier Vodafone told its subscribers with the Apple iPhone 4S to wait before updating to iOS 6.1 because of connectivity issues that owners were experiencing. After installing the update, some iPhone 4S users could not connect to the internet, or even make or take phone calls, or use text messages. iOS 6.1.1 was supposed to take care of the new problems, but now there are other issues.
Users posting on the Apple Support Communities forum claim that since installing iOS 6.1.1, battery life has been awful. Also the handset has been running hot. One user says that his battery life has dropped since the update from 7 hours to 5 hours. Another says that battery life on his iPhone 4S has dropped to 4 hours since the update.
The good news is that the connectivity issues are repaired. We can expect another update to fix these problems. Hopefully very soon.
Source Phone Arena
Have a look at the difference between the iPhone 4 and iPhone 4S.