Dropbox just works. Go on vacation, my itinerary, all my travel docs, critical material, it's in Dropbox, and often available offline, since wifi can be spotty. Now its in my phone and my Ipad as well. It just works. And if you're cheap like me, you manage Dropbox, not waste it.

But iCloud is the sleeper. In particular, Notes seems to be open on my desktop and all my devices. A terrific application.