For me the biggest misssing feature of all approaches to online folder synchronisation (including Dropbox, in a sad way) is secure backend encryption. For me, this includes an open source client and a free choice, where to store my files. Ideally I could have several decrypting clients to work with my files, while an arbitrary amount of encrypted clients would store my files on various backends, one of which could be a company offering this as service.
It seems like Gitdocs fits the requirement for encryption. Just use git+ssh for the remote of the repo, and transfers will be encrypted. Then, I guess, you need to set up ecryptfs or something on the server side so that things are encrypted on-disk, and then you can back up the encrypted files.
