iOS does not provide a way for administrators to block users from updating their operating system. It's never needed it until now. Today, though, I regard it as a critically missing piece of a large-scale iOS deployment.
When iOS was a simpler beast, I tried to see beyond what we had "lost" in terms of, say, multitasking in order to appreciate what we had gained in these other areas I mentioned in the first paragraph. Today, we have regained much of the power but are in danger of losing one of the main pillars of what made iOS great in the first place.
In terms of features and capabilities, iOS 8 brings me a lot of optimism. In terms of robustness, stability and reliability, it's giving me new reasons to worry.
I'd be completely fine if iOS and Mac OS X went to an 18 month development cycle. iOS needs a "Snow Leopard" release.