Some iPhone 4S and iPad 3 owners are reporting that their Wi-Fi is being "greyed out" or disabled after installing iOS 6. A thread about the issue on the Apple Support forums has already reached 93 pages. Users are reporting that their Wi-Fi settings are either disabled, or that they can't connect and are being forced to use a cellular data connection only. There have also been complaints about the problem affecting Bluetooth capabilities as well.
Early iOS 6 users did suffer from Wi-Fi issues when it was originally launched on September 19, however, Apple has fixed the problem. Two users have replied that Apple is aware of the new issue, but the Wi-Fi complaints are still piling up. The Apple Support thread has over 900 replies at the time of this post.