There's no way I would classify YouTube as a working app on iOS 8, at least not the iPad version. It's barely usable. Videos refuse to load most of the time, and when they do it's very poor quality even though I have a great network connection. After watching a video for over 5 minutes the app totally refuses any user input and it is super unstable. I downgraded my iPad back to iOS 7 because around 50% of what I use my iPad for is YouTube.
And what about on iPhone?