Hey there.
I just got iOS 9 for my iPad Air and it's amazing. I was wondering about my iPhone 5 though, should I update? Does it work properly? I heard that one of the main features of iOS 9 is compatibility so what do you say?
Sure. It's great! No issues whatsoever on my iPad mini 1. I think your 5 will be fine since it's to old to be affected by the Metal performance issues that plague the newer 64bit devices.