I'm either extremely tolerant or the luckiest guy on earth because I haven't had one hiccup with iOS 9 from day one. Same for El Capitan, Yosemite, or iOS 8. I just don't see them. Again, I'm not denying it happens, but it doesn't to me. On topic, the iPad Air 2 I have flies under 9.2, but it's no different than any other iOS 9 version I've had.
I don't think I'm that tolerant (because I'm the first to complain with slow internet and inconviencies or annoyances and I haven't seen any in the past two major releases on iOS and OS X). I guess my iPhone 6 and iPad Air 2 are really good, and my 2014 13" rMBP is flawless.
Again, I'm not saying there isn't problems but maybe they aren't as widespread as some would believe due to reviews and people's comments. It's just that people complain louder and more noticeably than they praise when things do work. For most people, when things work they just stay quiet and no need to say anything. But when something doesn't work they have no problem speaking up.