Apple's Claim That Nearly Half Of iPhone Users Are Already Using iOS 8 Is Slightly Misleading
But that statistic may be slightly misleading.
According to the updated App Store Distribution page, Apple is measuring the number of people who have upgraded by analyzing the traffic to its mobile App Store. While that does give a general indication of who is using which version of iOS, it ignores a large number of Apple's customers - the ones who don't use the App Store very often.
As 9to5Mac points out, most people who visit the App Store will be ahead of the curve when it comes to installing the latest updates. The chart Apple displays is probably showing a higher rate of adoption for iOS 8 than you'd find in real life, because it is measuring the most active, early-adopting users. Most iPhone users haven't connected to the App Store recently.
A 2013 survey discovered that 65.5% of US smartphone owners download a grand total of zero apps per month. So if you connect to the App Store and download an app, you're in the minority. While Apple's chart gives an indicator that its early adopters have taken to the new software, it doesn't account for the large number of people who haven't paid a visit to the App Store since the latest update was released on Sept. 17.
Generally, however, over time Apple does successfully migrate the vast majority of its users to its newest mobile operating system.