Since the iOS 8 original launch back in September of last year, along side the iPhone 6 and iPhone 6 Plus, it has seen a slowish rate of adoption, but now the growth is picking up.
As of January 5th 2015, the rate of adoption of iOS has hit 68%, which is a four percent increase from December 23rd. Apple has also seen strong performance over the holiday period, with a fair of device activations, which helped add to the iOS user base. When iOS 8 launched, it caused a few issues for Apple, such as the huge amount of storage space needed to install the operating system on devices with less storage, but this is something which has affected iOS 8 installs less as time has gone on.
Over the past few months, a significant amount of updates have been released. With iOS 8.1, iOS 8.1.1 and iOS 8.1.2. The next update is expected to be iOS 8.2, which will bring the usual bug fixes and the upcoming support for the Apple Watch.