Personally, I've been using Yosemite and iOS 8 every day. iOS 8 - no complaints whatsoever, at least on iPhone 5 and 6. I've heard some people complain that on

Personally, I've been using Yosemite and iOS 8 every day. iOS 8 - no complaints whatsoever, at least on iPhone 5 and 6. I've heard some people complain that on iPhone 4/4S it could be slow but that's a few years old hardware and Apple probably doesn't spend the majority of their time optimizing that most likely. Yosemite - major bug is that my WiFi stops working once in a whole (~once a day) and have to turn it off/on. Overall, I think the the criticism is definitely a little bit overblown.