Apple today released iOS 9.0.2 which contains bug fixes and improvements including:

• 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

For information on the security content of this update: http://support.apple.com/kb/HT1222