They probably didn't address user experience because that is difficult to quantify. They could've given their experience, but it would be just that... THEIR experience. If they were reviewing iOS 9.x on an iPad 2 and their experience was that it was surprisingly useable, that would not be helpful to you as YOUR experience is that your iPad 2 is UNUSABLE with iOS 9.x. Your first-hand experience supersedes theirs.
Every iPad that I've ever purchased (1, 2, 4, Air 2, 12.9 iPP) is still in regular use today.
The iPad 2 w/iOS 9 is indeed impressively still usable. But if I had my choice, I'd like to be able to downgrade it to iOS 6.x.
The iPad 1 running iOS 5 can obviously do less but what it does it still does as smoothly and responsively as they day it was new.