It is definitely a difference, even on the iPhone 6s (e.g. the animation for AirDrop in Control Center previously lagged, now it doesn't anymore). This is exactly how iOS 9.0 was supposed to be. Strange that it always seems to go that way: the final release of a major version sucks, after a few .x updates it's all buttery smooth. That just shows that Apple does have the people to make their software run incredibly well. It only takes quite some more time.
Anyway, I'm all happy with this release. And it's still a beta. Final release might be even better.