I'm excited and nervous for iOS 9 for my iPhone 6 and my iPad 4. Right now I'm on 8.4 on my iPhone 6 keeping the door open for a jailbreak. I hope you guys can give a good mini review on the performance of GM for the iPhone 6. I really hope performance is at the very least up to par with 8.4. I played with the beta and I came away feeling that if the GM is the same I'm going to stick on 8.4 until the iPhone 7 next year!
Right now 8.4 is great for what I use my 6 for. My only complaint is the music app doing the 2-5 second lag thing after playing music for awhile. It's a real bug that affects everyone and its still not fixed on 8.4.1 as I can get my iPad 4 to do it as well.
I'm starting to believe that it's true that you should leave the major iOS version your phone came with on it for the duration you have it to enjoy the best performance! I'm sure the 6s will run iOS 9 great as they are probably programming it specifically to run the best on that hardware. All the other devices seem to be getting sloppy seconds in the past and its annoying!
Every upgrade with my iPad 4 has been a true downgrade with overall performance with basic things like safari browsing! iOS 6 was lighting quick with safari and now with 8.4.1 it's laggy with the scrolling and it takes much more time to load web pages. I really wish I could go back to 6 on it. Lesson learned!
Anyways I'm still holding out hope that Apple is true to their word about performance this time with iOS 9. So far the beta has been disappointing. And I can't stand the new font! It's not cleaner or easier to read IMO. I end up staring at the letters and thinking about them and how weird they look and I feel like I installed a crappy font on bytafont that I can't delete right away! I might become one of those people who have the red 1 badge on their settings app for a long time to come!
Another problem I have is the FaceTime camera shifting problem. I'm really thinking about sending it in again (that's a whole other story...4th time camera shifting problem) before the warranty is up but then I know it will come back with that goofy font and iOS 9. But also when I go to sell my 6 next year I don't want it to feature that little foam washer in the camera too for someone to look at and say I don't want that! Decisions decisions.