Apple has given its first glimpse, though a bit vague, into iOS 8 adoption.
According to data on the Apple Developer Support Page, nearly half (46%) of Apple mobile devices that accessed the App Store on Sept. 21 were using iOS 8. That was four days after iOS 8 rolled out and two days after the iPhone 6 and iPhone 6 Plus officially went on sale.
While that may sound like a shockingly high adoption rate, it's important to keep in mind that the 46% figure does not represent the percentage of total Apple users with iOS 8 installed, but rather the percentage of users who accessed Apple's App Store on one particular day.
Initial estimates from third-party services suggested that iOS 8 adoption was slower than iOS 7 at the same point a year earlier. Some suggested it might be because iOS 8 was a less radical overhaul over iOS 7 than iOS 7 was over iOS 6, not to mention the fact that the latest operating system required more free storage space to download over the air.