iPhone 5s iOS 9 Update: 10 Things to Know After Three Weeks

You Can No Longer Downgrade to iOS 8

If you do decide to make the move from iOS 8 (or whatever you're on), know that there is no going back. Apple's closed off the iOS 8 downgrade loophole and you're stuck with either iOS 9.0.1 or iOS 9.0.2. 

Apple typically shuts down the downgrade loophole a week or two after an update's release so we could see the iOS 9.0.1 downgrade disappear at any time. iPhone 5s users, you should be on your toes as we push into October.