I work on ScoreMobile and we're at 79%. Probably over 80% by now.

60% of Pocket users in five days. http://getpocket.com/blog/2012/09/more-than-60-of-pockets-da...

http://david-smith.org/iosversionstats/

http://insights.chitika.com/2012/ios-by-device/

The Build & Analyze podcasts (which the author of The Magazine hosts) has talked about it multiple times http://5by5.tv/buildanalyze/96

I do appear to have overstated the 80% number but at this point in time but by the end of the year I'd be shocked if it wasn't over 80% based on the rate of adoption and then number of iPhone 5 being sold.

The folks behind Discovr Music say they're at 77% iOS 6 adoption: http://discovr.info/2012/10/discovr-ios-6-adoption-tops-77-i...