I published this article today explaining that at least one reason for the iOS 12 faster adoption is because it’s been long enough since iOS 7 and the last few releases have been stable enough that people are more trusting of updates again. This is the first year since iOS 7 that I haven’t had a single person ask me if it’s “safe”. What’s been your experience?
Many of the people I know went on the public beta, and I think the general public feeling is that (at least in part of this massive beta) that newly released versions are more stable.
One other data point is iOS’s more plaintive urging people to update than with previous versions.
I think the battery slow down issue got a lot of press, and the press picked up on this release as being a speed up instead of a perceived slow down. I know several people that were jumping on the update for those reasons. I also agree with @bowline that the public beta also got a lot of good press in general that I think reached the regular end users base.
I had a few people who all they knew about iOS12 was that it would make their phones faster so they downloaded it pretty quickly.
Looking at my own users, I still have quite a few on 11.4.1 but maybe that will change soon.
My guess is that as the OS gets more mature people do feel safer updating to it, and there has been no real news around issues with 12
I know many people just upgraded because it’s a performance focused release not backed with major new features or changes. I personally upgraded the family phones that are old, to befenefit from the enhanced performance.