"iCloud stores your music, photos, apps, calendars, documents, and more. And wirelessly pushes them to all your devices — automatically. It’s the easiest way to manage your content. Because now you don’t have to."
And indeed after the installation, i just added an iCloud account in the "Mail, Contacts & Calendar" preferences panes and thats pretty much all you see of it, at a first glance.
Mail, Address Book and iCal are ready to go and with iOS5 on my iPad2 everything is in perfect sync.
While this is nothing really new, you can achieve this with gmail or an exchange server with ease, iCloud is more then meets the eye.
Every Developer can integrate iCloud with ease in his applications and can backup/sync application settings, files and states in the cloud.
iOS applications get synched by default over the cloud. When i play a game on my iPhone4 and quit it i can continue playing at the exact same spot on my iPad. Same for applications like Keynote, do some touchups on the iPhone finish at home on the iPad.
Everything you purchased(or downloaded for free) from iTunes is also in the cloud, redownload your music or applications at any time without paying again. You can use em on all your devices as well without any costs. For your personal data, like application files and settings, you get 5gb for free while having the option to purchase more. iTunes Music, Applications have no space limit at all, same for pictures in the photo stream (soon more when i finished downloading new iPhoto beta).
Looks iCloud can keep what MobileMe promised: it just works!