I wouldn't say that. iOS 9.1 is still definitely worse than iOS 8.4.1 was on both my iPhone 6 and iPad mini 2. That app switcher is the laggiest thing I've ever seen. It suffers on my iPhone 6 (usually when going into or out of an app when a keyboard is open, messages does it the most) and going back to the home screen stutters at times, too. My iPad mini 2? Every single in and out animation is <25FPS if there are more than 3 apps in the switcher. Scrolling is stuttery, especially near the home screen. Swiping away apps is about 30FPS if there are blurred apps in the background. It's awful. Air 2 isn't quite as bad but it still has problems from what I've heard, probably similar to what I described on my iPhone 6.
Control Center suffers on both my iPad mini 2 and iPhone 6, still. Little delays when tapping apps still. Spotlight has that hesitation mid-animation if you slide down too quickly. I hardly see a difference from 9.0 to 9.1. There is some improvement, but nothing really to be said.