People started complaining about "lags" (that is not lags but just different animations) when iOS 7 was introduced. Now they have forgot it and suddenly iOS 7 was the perfect operative system.... Every year the same song.
iOS 7 was crash-prone but was still very responsive from iPhone 4S onwards (just like it had been since iOS 1)
iOS 8 is less crash-prone but definitely less responsive on all iDevices. In the sense that it is inconsistent. 3/10 times, a particular tap on a button will take significantly longer to register. But all the Apple paid comparisons will tell you how blazing fast iOS 8 is compared to iOS 7. But when it lags for no reason, is the time some people notice. I would love to see repeated tests to measure responsiveness. But Apple paid/sponsored (sarcasm obviously) will never dare to publish results of repeated tests as it will mean bye bye to all Apple's future events.
/rant