I guess I'm not sure what to make of some unknown-to-me company's study on usage of its own SDK for cloud storage; and this study being posted in 'news release'-style on their blog. To me, these are huge grains of salt.
Adding this layer of middleware is just another layer of complexity for us.
That doesn't include Amazon's unlimited free storage for photos with our family prime account.
Oh, and a 1 TB Western Digital personal cloud drive...
I don't think you can compare iCloud with general purpose storage; it seems angled towards iOS app integrations instead.
It's really handy - I've pretty much stopped using Dropbox, except to share files with people on other platforms.
With a few (and lessening) limitations, iCloud is becoming the general user-accessible filesystem that iOS has lacked since the beginning.
All that's needed now is a download manager in safari.
On iOS, the iCloud Drive app lets you see everything in iCloud storage as well.
Certainly iOS app integration is important in iCloud, but it functions perfectly well for any other use too.