Bump, the folks behind that iPhone app that allows you to quickly and easily exchange contacts, released a set of stats about its users that says almost 90% of iOS device owners are already running some version of iOS 4.0 or above. Bump reportedly has over 25 million downloads, so we are talking about a decent sample of the iOS user population (though I'd argue that it's not quite as widespread as the stats might be on an app like Angry Birds -- still, we'll take what we can get). According to their figures, over 89% of users are running iOS 4.0, a number that's a little higher than what I've heard from developers in the past.
Bump says that 10% of its users are still running some form of iOS 3.0, and just 2% of users are stuck back on iOS 2.0. Within the 4.0 crowd, 52.89% are running the latest version of 4.2.1, with 27.5% still running 4.1.
Why's everybody so caught up? In addition to the press around each update, I'd suggest that the holidays were probably a big equalizer, with new iPhones and iPod touches smoothing out the playing field (since they come updated with the latest version automatically). With so many people all caught up to iOS 4.0 on the same hardware, Apple has a nice solid platform to build on, something that Android phones have been struggling with on both the hardware and software fronts.