I currently have an iPhone 6 Plus running on iOS 8.4 latest beta. The device is lagging and I have to reboot it a lot. I am wondering how is iOS 9. Is it running better than iOS 8 on iPhone 6 Plus, or worse. I know iOS 9 is still in Beta, actually Dev Beta but it shows signs of how the final OS will look like. I hate nothing more than lag, because of how buggy iOS 8 was on iPad Air I decided to leave mine on 7.1.2. Same for my iPhone 5S it's still on iOS 7. I would rather not have a new feature, even if it's a major one over having a laggy device to deal with.