A friend of mine has an iPad mini 1. They left it on iOS 7 for the longest time as I advised because I didn't want them to cripple their device, and they didn't either. The other day they randomly updated it to iOS 9, and it performed better than I expected. Somewhat better than my iPad mini 2 in a couple areas...
Sliding down for spotlight-the blurring effect. Perfectly smooth, couldn't be better. On my iPad mini 2? It's pretty good, better than 8. But it hovers around 30-40 fps. Keyboard popping up is smooth on both as long as you don't slide down too fast. Now the big deal. The app switcher. Almost 100% smooth on the mini 1, scrolling is pretty good, going into the app switcher is fine, but going out of it can sometimes cause some stutter. My iPad however? Stutter everywhere, entering and exiting the switcher is the worst though. Probably 20FPS.
I just couldn't leave this out of mind. How does Apple let this happen??