It was showcased and offered for download at the end of January, but just over a week later, iOS 6.1 is causing some controversy.This seems strange, as the widely held view is that 6.1 doesn't change things massively. Added LTE support, more languages for Siri, a change to iTunes Match and the option to buy tickets in the US via Fandango. Not exactly reinventing the wheel.But it's enough to cause problems for some iPhone owners. Vodafone has sent out a text message to iPhone 4S users, saying: 'If you've not already downloaded iOS 6.1 for your iPhone 4S, please hold off for the next version while Apple fixes 3G performance issues.'It's interesting that Vodafone has gone public with this, which you would guess is based on feedback from customers already upgrading and its own investigation. Apple's support forums are also coming up with issues post-upgrade, specifically pointing to battery and overheating issues. Those have yet to be officially confirmed, but it does add to the concern.Apple is obviously working on a new version of the software (iOS 6.1.1 you would guess). If you've not yet upgraded, sit tight. If you have, let's hope Apple is working with some haste.