iPad Air 2 and 6 Plus are running much better on 11.1 beta 1.My iPad Air 2 is running fine with iOS 11, performance and battery is OK. Opening Apps on my iPhone 6 Plus is extremely slow compared to iOS 10.3.3 and battery around 20% weaker.
6 Plus sped up a lot. Still needs some tweaking, but much better than 11.01. By time beta is over, should be real good.