Two generations behind for this one here (iPad 3, first one with retina display). I don't feel so bad seeing there's lots of people upgrading from the iPad Air models...
We have 3x iPad 3s at home. Upgraded one to iOS 7, then 8 and it's awful. Much, much, much slower than iOS 6 even with animations disabled. Haven't gotten around to upgrading it to iOS 9 yet. I've kept the other iPad 3s on iOS 6 because of poor performance on newer firmware.Ho boy that's a nice upgrade. My iPad 3 felt slow the day I bought it. Goodness knows how it is with iOS 9 these days