Ditto - I was very confused, but I quickly figured out: it's not for me. Apple seemed to imply it was wonderful, magical, etc - so I figured this must be even better than Dropbox. It's not. It's basically a super-limited subset of file sync, combined with a contacts / calendar sync (for iDevices) and a way to upload your iDevice photos automatically.
I opened an iCloud account, tried to sync something, then realised that:
(a) doesnt work with my Android phone wrt contacts sync
(b) file storage for iWorks apps only, not general purpose. I don't use any iWorks apps.
(c) I couldn't easily see what's synchronised where (unlike Dropbox), and what's local only, but it doesn't matter because it's not really cross-platform anyway
(d) when I wanted to stop iCloud sharing is gave some dire warning about how it would delete my data. Not explaining if this would only be deleted from the cloud, wiped from my local machine, both, or what.
From what I understand, it's only interesting if both of the following are true:
(a) you own more than one Apple device
(b) you use Apple applications for most of your productivity
(c) you have a great fear understanding files
Andy Ithnako and other fervent Apple supporters are even having problems.
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This weeks Macbreak Weekly (274) podcast gives some mention to the (great lack) of clear documentation for developers.