Dan Moren starts his experience with iCloud this way.

Your data is in sync across all your devices, changes update immediately, and you never get a single error message.

It has never been my experience with iCloud - sync takes ages in the always-connected cloud world of today. Especially when I compare it with Dropbox and Google Cloud, the services that I use.

I am a big, big fan of Dropbox. The service has got the perfect balance of functionality and performance. Everything just works.