Install It If You Use Live Photos
If you're an avid Live Photos user (Live Photos is a feature found on the iPhone 6s and iPhone 6s Plus), you'll want to consider downloading the iOS 9.1 update right now because it brings some useful upgrades to the camera feature.
With iOS 9.1 on board, the iPhone 6s "now intelligently senses when you raise or lower your iPhone, so that Live Photos will automatically not record these movements." So, Live Photos should be a whole lot better than they were with the other versions of iOS 9 on board.
Also of note: iOS 9.1 also delivers Live Photos APIs which will be important for the feature's future on the iPhone 6s and iPhone 6s Plus.