Cloud storage: iPad loses
IT may hate it, but the ability to keep documents in the cloud is amazingly useful. Apple's iCloud Documents feature lets you keep documents in the cloud, but in a much too limited way to be very useful. It works only on iOS and OS X, and you need the same app on each device to access the same document; for example, only Keynote can open Keynote files. And though Keynote can open and save PowerPoint files, it can't save them to iCloud Documents from the iPad (on the Mac, you have to copy the PowerPoint into iCloud, not save directly).
The boundaries of iCloud Documents are simply too tight to be used outside of Apple's iWork suite. Use Dropbox or Box instead.