Apple has just released iOS 9.0.2 with bug fixes and performance improvements.Last week apple released iOS 9.0.1 to fix bugs discovered after public release of iOS 9. Apple has also stopped signing iOS 8.4, which means downgrades from iOS 9 are no longer possible. Those who wish to restore their iPhone, iPad or iPod touch to iOS 8.4.x will not be able to do so and they must upgrade to iOS 9.0.2. Below is the changelog of iOS 9.0.2 and direct download links to iOS 9.0.2 for iPhone, iPad and iPod touch.
iOS 9.0.2 changelog
Fixes an issue with the setting to turn on or off app cellular data usage
Resolves an issue that prevented iMessage activation for some users.
Resolves an issue where an iCloud Backup could be interrupted after starting a manual backup
Fixes an issue where the screen could incorrectly rotate when receiving notifications
Improves the stability of Podcasts
To upgrade your iPhone, iPad or iPod touch to iOS 9.0.2, go to Settings > General > Software Update. Tap Download and Install to start the upgrade process.
You can also download iOS 9.0.2 IPSW if you wish to upgrade your device using the IPSW. You can use the IPSW as many time you want in future to restore your device to iOS 9.0.2.
How to upgrade to iOS 9.0.2 using IPSW.
To proceed, download iOS 9.0.2 IPSW file from the links given below. Open iTunes. Take backup of your device. After backup has been performed, press Shift key on PC or Alt key on Mac and click on Restore button in iTunes. Browse to the IPSW file you downloaded and select it. Wait till your device is upgraded to iOS 9.0.2.