iCloud Drive and iOS 8
With the recent iOS 8 release, Apple have introduced a new feature called iCloud Drive. This is a bit like Dropbox and promises to be a better way to interface to iCloud itself.
Unfortunately once enabled, all of your files are migrated and they become inaccessible to any device NOT running iOS 8, or the soon to be released Yosemite (OS X). This makes it a bit of a problem for apps that need compatibility between multiple OS versions.
For now I would STRONGLY ENCOURAGE you to hold off enabling iCloud Drive, unless you can do without iCloud support in my apps.
Having said that, it appears as if iCloud Drive does work, but clearly only between iOS 8 devices.
Please see Apple’s FAQ on iCloud Drive.