I recently started using Phabricator fairly heavily for a review of a large patchset, and I am less than impressed. It could be that the project where I'm using Phabricator didn't set up their review system properly, it could be related to them running svn, etc. And it could certainly be due to my having used Gerrit for 2+ years and Phabricator for a few months. That said..

The problem I have with Phabricator can be summed up in saying that it is a review system which is not tightly integrated with the repo, and that approach has inherent problems. If you actually want to apply the patchset under review in order to run it (or even look at it with other tools), arcanist does not seem to be helpful in finding the correct revision of the tree. You have to communicate with the author via side channels to determine what version of the tree they were running when the patch was created. When arc patch blows up, it is not clear how to recover (picture a git merge with no obvious way to resolve conflicts). I finally got a pointer to the author's git repo and cloned it..

I find it a bit disingenuous that the essay first compares Phabricator to Github pull based workflows, and to gerrit. They go on to criticize pull based workflows, but fail to mention that Gerrit is not a pull based workflow, and gives the same advantages of Phabricator (squashed, linear history). Gerrit has the advantage of being tightly integrated with a repo, and being able to easily fetch the author's work so you can look at it in context, test it, etc.