http://seafile.com/en/product/private_server/
I've been using it for a few months hosted on a vultr vps. All files are encrypted on the clients, and there are no limits. From what I've seen, it doesn't fall into the upgrade issues that owncloud has seen.
I use Seafile for personal data sync and I couldn't be happier. It is great!
Been using it for close to a year now and very satisfied with it. Only upgraded a couple of times and no problems so far. Major selling points for me: ability to select any number of different folders to sync, ability to connect to any number of servers (i.e. at work I connect to both my personal server and the one which backs up my job related files), seems plenty fast
I've been playing with Owncloud, but I read a lot of horror stories about it this week.