Dropbox works equally well across platforms with near 0 synchronization issues. It's just a folder. They aren't trying to add cloud to their own platform, they don't care what device you use or if you use Apple's word processor or Microsoft or Google Docs.

Dropbox has has a firebase/Parse style API you can use to build applications that store that application data in the cloud.

My favorite Dropbox API uses:

automatic syncing of O'reilly Media books. Whenever O'reilly updates one of their ebooks, I always have the current copy, because O'reilly syncs it with Dropbox.

1Password synching.

automatic Hackpad backups (they had that even before they were bought).

I installed this new app the other day, Trickster from the Mac App store, it automatically detected I was using Dropbox.

But I'll mention some negatives:

Those new recent android apps were really bad and I uninstalled them. Carousel and that other one, I don't even remember what it was now. They were just terrible apps, at least on my Galaxy S4.