I would like to think this would begin to gain ground against systems like Jira (oh, how I loathe thee). Sure, Phabricator is a bit of a pain in the ass to set up in its current state, but it seems to be head and shoulders above many in both features and ease-of-use (not to mention price).
I'm not a Jira fan, but TCO usually includes more than just the actual price of the product. So e.g. setup, maintenance and ongoing support. :)
It's unclear to me why this is "by Facebook." Nice concept, though.
Thanks, I missed the repo link! Someone seems to have edited "by Facebook" out of the submission title, but Phabricator does appear to be owned by their Github acct.