I think there's another point to be learned from both the Dropbox comment and CmdrTaco's original infamous iPod take. And that's the importance of a really well-designed product that's simple and easy to use. Both Dropbox and the iPod weren't the first to try to solve the problems they were addressing, but they were the most elegant, intuitive solution. Both implementations effectively got out of the way of their users and exposed the underlying function with a little impedance as possible. It's always important to remember that the goal isn't for users to use your product. The goal is for users to get the value your product delivers. That sounds obvious, but a lot of product development teams forget that. Both Dropbox and the original iPod seem to embody that distinction.

As for your "nothing I can deploy on my own server" comment, checkout syncthing or Resilio. Both take a bit more doing than a simple Dropbox install, but I've found syncthing to be pretty bulletproof once it's configured and I've heard a lot of people prefer Resilio.