I use http://owncloud.org and am quite happy. But also happy for more competition :-)
Does it work fast for you? Do you use desktop client or primarily web GUI?
My server was a Core i7 with 12GBs of RAM, SSD backing and a more or less dedicated NAS. I tried with both SQLite and MySQL backing. MySQL was better, but still unacceptable. If that's not enough to run it for a single user, I can't imagine what it's like trying to deploy it for a full family, even less an organization.
I love the idea behind owncloud, and I admit touting it myself in my own "honeymoon phase", but in hindsight I have no problem admitting that the execution is just too poor.
It took it about 1h to sync a folder with about 100 files, under 30MB total across 4 computers. Not to mention that minor modifications appeared only after 15 minutes (small text files).
BTSync worked great, but I wouldn't trust it with something sensitive.
What did you end up using?
Long story short, I went from an "all cloud" (Google + Dropbox) setup to a "all mine, no NSA" setup. Now I've decided that counter zealotry doesn't have that much for it, and I'll try to balance privacy with best of breed services, without trying to end up with all my eggs in one basket. Not doing that ensures I keep interop and portability in mind.
My end-result is calendar via Google (only solution I can get collaboration and invites working properly), files via Dropbox, mail with Fastmail (much better than Gmail) and contacts via Baikal on my own hosted server.
Fastmail is adding support for calendering and contacts via CalDAV and CardDAV, but I've yet to fully investigate that.
It's a moving target for me, but currently it's been stable for a few months, and I'm mostly happy.