According to Apple's developer webpage, iOS 9.0.2 update (released last week) has bumped up adoption of the operating system to 66 percent on compatible devices — based on Apple App Store measurements as of Nov. 2. That compares to 57 percent a month ago.
iOS 8 is on 25 percent of compatible devices, while nine percent of iPhones and iPads are running an earlier version of the operating system. iOS 9.0.2 was released on Sept. 30. It resolved several issues and improved stability, according to Apple.