Sometimes I get out my old iPhone 4S and iPad 1 (1st generation!) on iOS 6 and 5, respective, just to remind myself how good it was.
Despite having much slower hardware, iOS flies on them and registers input very consistently.
The best I ever used was an iPhone 5 on iOS 6 -- probably the fastest iOS device there has ever been.
I had a 4s and stuck with iOS 6 for a long, long time. I eventually caved due to software requirements and I've lived with that pain ever since. What a pile of garbage iOS 7 was on a 4s or earlier device. I still think Apple should allow anyone with that old of a device to revert to iOS 6, or at the very least, give them a "lite" version so it returns to something that you can actually USE.