I've been using it for a year. Works great. One of the most thoughtfully designed and complete bits of software I've ever run into.

I'm especially delighted with it's self monitoring and the status change email messages it sends me.

That it includes webmail and gives me a nicely featured DNS server only makes it a touch more awesome.

I run it at Digital Ocean for ten bucks a month. I support family and friends. My email does not pass through google or microsoft servers and that makes me very happy.