I'm running the 9.1 Beta 1 (13B5110e) on a 128GB iPhone 6. And have uncovered some critters.
Photos app
Under the Shared folder, when I select (touch) an image in my Shared stream, instead of the image going full screen, it turns blurry, the app locks up for about 5 seconds and then crashes back to the Home screen. I can replicate this every time. Feedback sent to Apple. Side note: their feedback submission app is really well done.
Calendar app
When rotating from portrait to landscape view, my landscape view calendar is completely empty (unlike my incredibly full portrait view). The only solve has been rotating back to portrait and then immediately back to landscape again. Upon second rotation, landscape calendar matches the full calendar as seen in portrait. Can replicate this every time. Feedback also sent to Apple.
Grabbing the Beta 2 now. Curious to see if it addresses any of the above hiccups.
Overall, iOS 9 it's pretty solid upgrade. The emphasis on intelligence and proactivity yield some pretty impressive/useful results. Hopping in my car, iPhone now presents an estimated time of arrival at the office (as one example). Would be neat to see Watch present this same info. Sticking with Maps, I like the new warning about unexpected delays ahead and the offer of an alternate route that will save me X number of minutes. Has already proven super valuable for me. Unfortunately, Denver is not yet seeing Transit activated. Looking forward to that one. Battery life does seem noticeably improved. And don't sleep on that little Notes app. The updates yield a much more useful tool (coming from a fairly heavy Notes user).
Cheers.