Can't get from iOS 6 beta/preview (GM) to iOS 6 final release

I took advantage of a tutorial online and gained access to the iOS 6 golden master beta last week after the iPhone 5 announcement (this is on my 4S). Now that iOS 6 is officially out, I'd like to update the software to whatever Apple just released, rather than being on beta software (even though the beta is probably 99.9% where the release is). Can anybody advise me as to how to either get back to iOS 5 and then update, or get straight to iOS 6?

One option I've been hoping for is just downloading the update from Apple.com, via this page: http://support.apple.com/kb/DL1578. However there's no actual download available, just a change log. If I could get the .ipsw file, I could just alt-click "Restore" in iTunes, then update my iPhone with that - but I can't right now.

Any suggestions/help would be appreciated.