I have been using iOS 9 since a week. These are the list of features/ improvements that I really like:
- Back to app link when redirecting from one app to another. Super useful and I wish they had added this a long time back. Interestingly, this is my top iOS 9 improvement.
- iCloud Drive as app on iOS. I was always contemplating moving out of Dropbox. The deal is sealed now.
- Notes. I am using Evernote for everything but have switched to Notes for my most immediate and important notes. Now, I see Evernote as more of a filing cabinet. My freshest and most updated notes stay in Notes. I am digging the checklist and sketch functionality.
- A smarter Siri. I have started using Siri a lot - add reminders, open apps, add notes etc. Siri hardly gets anything wrong.
- Low power mode when your battery is below 20%.
- Six digit passcodes.
- Mail search has significantly improved.
- News app that potentially replaces Flipboard for me. I am sure there will be many more improvements to the News app. One caveat - I wish it would show me more tech related news under "For You".
- The new San Fransisco font is a nice touch.
Overall, I like the fact that these were incremental updates (except for Apple News) to iOS 8. The iOS experience feels much smarter. That's the way it should be. Make software better over time and not to try playing the features game. I rather have Apple work on tying all the lose ends (for e.g. saving an attachment to iCloud Drive on iOS, keyboard shortcuts over iCloud) to make the experience even seamless