My girlfriend had issues on the first day.... When she turned on Airdrop to try it out, her home button and power button stopped working and she couldn't navigate through her phone at all. We were out for dinner and I told her to put her phone away but she started complaining it was broken. So I said just leave the flashlight on, and bluetooth (Control Center was still swipe-able) and kill the battery til we get back to my car to charge it and reboot.
Eventually, that helped fix it, but her sisters iPhone 5 had to reset because the iOS Completely wiped out her memory, apps, and bugged her iMessage.
Then there's charging problems and all... After hearing their experience I am sticking to iOS 6....