I don't know if this has been brought up yet or not, it's a very long thread, sorry, but it's an absolute non-issue. iOS 7 was a huge update, everybody was talking about it, it brought life to the tried old OS and UI. If you saw iOS 7 on a friend's device and then picked up yours with 6 installed, chances are your eyes bled from it, an you rushed home to update. It was a cool new kid on the block. On the other hand, iOS 8 is a more "ordinary" update for most users. Most consumers don't follow tech news and unless they are compelled to, they update when the device (or a techy friend like many of us) nags them long enough to do it. Just like two years ago in the case of iOS 6. Look at this report:
http://www.cnet.com/news/ios-6-adoption-hits-61-percent-just-one-month-after-its-release/
After 4 weeks, iOS 6 adoption rate was at 61%. Now, iOS 8 is at 47% after two and a half weeks. I think that's an adoption rate comparable to, if not better than the last "ordinary" iOS update.