[xorcist]

The Wikimedia project and some other high profile projects use it.

I did a pretty thorough evaluation once which included Phrabricator, it came out very well, especially the work flow around code review. It wasn't chosen for unrelated reasons.

I don't know why it isn't more popular than it is. It seems to be very mature, certainly better than a lot of tools that organizations pay good money for.

[plorkyeran]

There's no one pushing phrabricator. No marketing means that most of the people picking a tool to use have never even heard of it, and it's not really something that a single developer can adopt and then champion internally.