iPhone 5 iOS 9.1 Problems
I haven't run into anything significant with the iPhone 5 iOS 9.1 update but that doesn't mean others haven't. There are iPhone 5 iOS 9.1 problems.
Current iOS 9.1 problems include issues with battery life, contacts, various applications, Wi-Fi, Bluetooth, and yes, lag. The encouraging thing is that these problems appear to be isolated to a few iPhone users. We haven't heard about or seen any widespread iOS 9.1 bugs or problems except for one.
If you set the update to install overnight, it might kill your alarms. The solution is to install the update when you can monitor it, not at night when you can't.