Apple has released iOS 6.1.1 for iPhone 4S devices, presumably fixing the 3G issues that a carriers warned their customers about with the iOS 6.1 update. The update comes with a build number of 10B145. It weighs in at a relatively paltry 23MB.
A beta of iOS 6.1.1 was released in the middle of last week carrying a build number of 10B311 — it’s likely the upgrade released today was a urgent bug fix and the prior 6.1.1 beta sent to developers will become 6.1.2.
Thanks to @AppleNicholas for the screenshot