I'll admit I was very nervous before I decided to upgrade my iP4 to iOS 5 because of my personal experience with what iOS 4 did to my old 3G. But I have to say iOS 5 runs great on my iP4. Been using it for 2 weeks now. Everything seems to be snappier and some of the lags that I saw with iOS 4.x seems to have disappeared. The phone runs very smooth over all. I couldn't be happier. So anybody that is still on the fence and who have not updated to iOS 5 should definitely update. It is a great update from Apple!