It turns out that their numbers might have been off because according to an official press release from Apple, it seems that iOS 9 has been installed on more than 50% of devices since its release. According to Phil Schiller, Apple’s SVP of Worldwide Marketing, “iOS 9 is also off to an amazing start, on pace to be downloaded by more users than any other software release in Apple’s history.”
It certainly would seem that way, especially given the various under-the-hood improvements and changes that Apple has made in iOS 9. However at the same time, there have been various user reports of problems with iOS 9. There are many threads on various forums where users are complaining that their devices feel laggy after the update.
There is also the issue of iOS 9 messing up push notifications in which in certain cases, push notifications aren’t even being delivered. In any case as is the case with first releases, there are bound to be bugs but hopefully Apple has a fix planned for the near future.