I'll whine only about the bugs.

Updating to iOS 6 pretty much killed my wife's iPhone 4. The sound on it start working in arbitrary fashion, only ringing, and occasionally making other sounds (i.e. sms, email and etc notifications) - that would work only 10% of the time. The only solution to that (after much shaman dancing) was to do a clean setup - restoring always brought back the same problems. Ended up getting her a 4S, where the restore didn't cause any problems, so I just sold the old 4.

On my 4S, the only issue I'm experiencing is that auto brightness does not work anymore, at least not as intended. I can live with that, by occasionally adjusting the brightness manually.