Vodafone UK subscribers with an iPhone 4S who haven't upgraded to iOS 6.1 may want to hold off on doing so. The carrier is currently sending out text messages to customers stating that there's a bug in the new firmware.
According to the warning, the issue has to due with 3G performance. Apparently 4S users on Vodafone UK have been experiencing problems with both cell service and battery life since updating to the latest version of iOS...