Yesterday afternoon, I put the first iOS6 beta on my iPhone 4S, and stayed on wifi the whole time. Today, I checked my AT&T bill and found that I had pulled 2.1GB of mobile data in just over four hours! I didn't think my mobile network was capable of such throughput, but I think it's either a measurement error, or iOS6 not stopping me from doing iCloud restore activities over the mobile network. Either way, it seems iOS6 is to blame. AT&T seems powerless to fix these while in the active billing cycle, so I guess I will be throttled when I hit the 3G mark in a few days. Despite what the release notes say, you CAN roll back to 5.1.1 using DFU mode, which is what I did for other reasons. The ironic twist? My Verizon iPad could not use wifi after the update to iOS6 so I rolled that back, too.