[NewsPoster]

Apple is trumpeting the launch of iOS 9 as an amazing success. In a release this morning announcing the availability of the iPhone at retail on Friday starting at 8AM, Phil Schiller, Apple's senior vice president of worldwide marketing, said that "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."

Apple claims that the operating system is on more than 50 percent of all active devices, as measured by App Store metrics on September 19. Unclear is what Apple calls an "active device." However, Apple's data is presumably more accurate than that measured by third parties last week on September 19, which suggested about a 25 percent adoption.

Early reports from users suggest that iOS 9 runs well on earlier supported hardware, due to lower RAM and storage requirements, but as with previous version of the operating system, some features are unavailable on older models.

[Inkling]

Not surprising. Apple is offering something most unusual, a major OS upgrade that gives a longer battery life and uses less memory. That is almost unheard of. And the 9.0 version runs on all the devices that ran iOS 8.0, Amazing! This is the fourth major iOS that runs on my iPad 3. Compare that to my Kindle 3, which only got a single, minor upgrade before Amazon abandoned it.

[I-ku-u]

Apple's metrics appear to count devices that actively talk to Apple's servers, which would undercount all active devices and thus overcount the adoption percentage. Third parties likely overcount active devices, by assuming any device not accounted for as 'elsewhere' is still used, and thus undercount the adoption percentage.

Worrying about which is (more) correct is however not the point. As long as both methods keep their methods consistent, then calculation of adoption rates and comparison between OS versions is meaningful.

[Makosuke]

@I-ku-u: As you say, as long as the methods are consistent, differing methodologies don't matter in comparing this to previous versions of the OS.

From a *developer* standpoint, however, I'd be much more interested in the percentage of "active" devices, since those are also going to be the ones downloading updates to my apps or buying new apps. If your iOS device never talks to the app store so Apple never sees it, you're probably also not using anything new I build, either.

[Steve Wilkinson]

Does anyone know about (or have experience with) backwards compatibility of iOS 9? I still have a iPod touch 4th gen in the mix (on iOS 6). It has basic enough iCloud support that I run Calendar, Contacts, Notes, etc on it and maintain 'sync' between all my devices. That still works with iOS 8 so long as I don't use the 'new' iCloud... but I'm curious about iOS 9. It's what is holding me back from updating so far. (Especially since I doubt Notes will be compatible... though I could let that one go, I guess.) (And yes, I do need to get a new iPod touch!)

Also, I'm curious if anyone has any reports for iOS 9 on the iPad 2. Does it make it more usable again? (especially keyboard input)
Thanks.

[Mike Wuerthele]

iOS 9 on the iPad 3 and 4 is pretty nice, actually. I'll be tossing it on a first gen mini a bit later today, which is very similar in performance to the iPad 2.

[Steve Wilkinson]

Just as a follow up... I've upgraded to iOS 9 and OSX El Cap on all my devices by that old iPod touch, and everything still seems fine. You just have to tell it not to use the new iCloud and not to go to the new Notes format. (It asks about both.)

@Mike, I updated my iPad 2 to iOS 9 as well, and I think it has improved a good bit (still laggy in the UI now and then, but generally better), but the keyboard input is still quite laggy. Unfortunately, that's kind of key, so I'd still give a low score. Since it's about the same or a bit better than iOS 8, it seems like a good move. But, I still wish I could go back to iOS 7... where the iPad 2 was still a pleasure to use.

At least for me, the iPad 2 is getting to be an older device. I'm curious about your first gen mini, but I think in that case, there could be some not-so-happy customers, as Apple was still selling those new not too long ago. Obsolete out of the box isn't a good user-experience!