Ever since Android has grown to become a real competitor to iOS, Apple has taken pride in the fact that its users are much quicker to upgrade to the latest version of its mobile operating system than Android users typically are.
While the fact that iOS handily beats Android in update speed is simply owed to Apple's less fragmented range of devices, last year's run on iOS 7 was impressive even by Apple's standards. iPhone and iPad users wer so keen on getting the radically redesigned operating system that Apple's servers were temporarily brought to their knees by the volume of update requests.
According to Mixpanel, iOS 7 adoption reached almost 40% within 48 hours, a number that Android KitKat, the latest version of Google's open operating system, doesn't even come close to matching almost one year after its release. This year though, Apple users seem less hurried to get their devices updated. Even though iOS 8 arguably adds more functions than iOS 7 did, only 33.5% of iDevice users have updated their phones/tablets seven days into the release. At the same time last year, the adotion rate of iOS 7 was almost twice as high. Apparently, last year's redesign was much more attractive to users than this year's added functionality is.
This chart compares the adoption rates of iOS 7 and iOS 8 in the first seven days after their respective releases.
You will find more statistics at Statista