Apple released the iOS 6.1 software update on January 28 2013 to users of various iPhone models including the iPhone 3GS, iPhone 4, iPhone 4S or iPhone 5.
However, after installing the update, iPhone 4S users have complained serious connectivity issues causing them to "occasionally experience difficulty in connecting to the network to make or receive calls or texts or to connect to the Internet." Many other took to Apple's forums to report a considerable deterioration in battery life of the said device.
Apple has now released iOS 6.1.1, a "bug-fix" version to sort out this issue that had caused a number of European phone operators such as those in UK and Austria, including Vodafone, to warn customers using the iPhone 4S not to update to iOS 6.1.
The new software release, a 968MB update is now available only to iPhone 4S users on their phones or can be downloaded via iTunes.
The notification screen specifically says, "This update fixes an issue that could impact cellular performance and reliability for iPhone 4S." So it's quite likely that the update will be restricted to the iPhone 4S only. Also, there was no specific mention of whether or not the iOS 6.1.1 update will resolve battery issues.
Carriers had begun warning users last week not to update to iOS 6.1 if they hadn't already done so, saying that 3G connectivity could be affected. It seems that iPhone 5 users have also complained of highly diminishing battery life with iOS 6, but Apple has not yet recognised this problem.
Here's a message posted by Vodafone UK regarding connectivity issues on the iPhone 4S:
We're aware of an issue caused by Apple iPhone 4S handsets that have been upgraded to iOS 6.1 which impacts performance on 3G.
Some customers may occasionally experience difficulty in connecting to the network to make or receive calls or texts or to connect to the Internet. Apple is working on a solution to their software issue. These connection problems are intermittent.
While Apple's investigations continue, we would recommend that anyone who has not yet installed iOS 6.1 on their iPhone 4s should delay doing so until Apple has confirmed that their problem has been fixed.