Perhaps from your perspective, although I don't know how extensively you've tested old and new features, or what apps you're running, but results clearly vary -- just look at the Apple Developer forums, there's only about a billion bug reports. And I've encountered most of those myself on iPhone 5s, iPad 4, and iPad mini 3. That said, it's good to hear that it's performing swimmingly on the Air 2, at least from your point of view--it gives me hope. Primarily I'm eager for an iOS 8 level of stability and Apple Music.