updated 12:56 pm EDT, Thu September 20, 2012
Wi-Fi issue already solved on Apple's end
Early users of iOS 6 have been encountering significant bugs, reports say. Initially, for instance, people complained that they were having Wi-Fi connectivity issues, triggering "page not found" errors in Safari and elsewhere. The glitch appears to have been linked to iOS 6's network verification technique, involving a webpage hosted by Apple, used to test Wi-Fi connectivity. The page appears to have gone down yesterday, but is now back up and working.
More serious problems have been encountered with the App Store. Some people, including at MacNN, have had trouble getting apps to update, and they may even stall partway through a download. In other cases people have been unable to view Passbook-connected apps when loading them through Passbook itself. A workaround involves going to the Date and Time section under Settings, disabling automatic time, and then setting the year ahead by one before trying to update again. If that doesn't work, turning automatic time back on may fix the problem.
Apple meanwhile appears to have solved an SMS exploit in iOS. The firmware supports optional features in SMS' User Data Header, including a "reply to" address; in iOS 5, a hacker was able to send texts to iPhones using any reply number they wanted. iOS 6 closes this hole.