I've totally stopped using any other file syncing app. No Onedrive, no Google Drive, no Dropbox.
Bit torrent sync is available on Windows, Linux, Mac, and Android. It's fast, easy to setup, easy to manage on an ongoing basis, secure, and because it's unlimited and flexible, I'm using it for things that most people wouldn't even thing of.
We use it at work to sync customer's encrypted backups to our site, where an Ubuntu vm puts the backups on a SAN.