In testing the new iCloud integration in Mountain Lion, a file could be open in multiple locations – say, your Mac, iPad and iPhone – and when a change was made, it would appear almost instantly across all three devices in real time. You don’t have to wait for a notification, or reload the file. It just appears. While the immediate thought is that iCloud is rapidly turning into Apple’s own, improved version of Dropbox, it’s also a fierce competitor to Google Docs, and the long-rumored Google Drive.
With Google, however, the philosophy is that file creation itself can be migrated to the cloud. An online office suite is “good enough,” if not as good, as a native one. And “good enough” will win due to ease of use. With almost a completely opposing view, Apple’s iCloud is doing the reverse: bringing the capabilities of the cloud to the richer, more robust native apps. This includes not just office apps in iWork, but through the use of developer APIs, it will extend to any apps that need to be iCloud-enabled. Although today, iCloud support is more limited for third-parties, the APIs will improve in time. Eventually, any app running on the Apple platform (desktop or mobile), will have the tools to move data between its different installations.
(TechCrunch, Apple’s iCloud Is No Dropbox Killer (It’s Much More))
As I've said before, iCloud has the potential to embody the server-client paradigm at its best: a concept Apple—though its implementation thus far has been technically underwhelming—has perfectly understood, while Google remains obstinately set in a web-centric environment.