For me, 8.4.1 is way smoother than beta 5 on my iPhone 6. The app switcher in beta 5 is smooth but the animation of tapping into app causes dropped frames. Control center is laggy and tapping an app from the home screen has a noticeable delay. Overall I feel like I'm waiting for things to happen more than I am with 8.4.1...things happen much faster on 8.4.1. I'm confident that beta 6/the GM will fix that though and I'm reserving judgement until the final version.