I've been using Phabricator for almost a year now in our company. At first, I also had my questions about the workflow with arcanist (the local PHP cli software to interact with Phabricator). However, right now I really love it and miss it on every repository which works without Phabricator. Commands like 'arc feature', 'arc tasks' and 'arc inlines' provide a solid abstraction over the repository to bring the workflow to the cli.

About the unit tests: indeed, out-of-the-box Phabricator only supports running them locally (you can configure the unit engine to run every time a piece of code is been send into review). Luckily, it's not that hard to hook into the event engine (https://secure.phabricator.com/book/phabricator/article/even...) to, for example, trigger your CI-server to run the test suite for a specific revision. Also, Phabricator is still being developed actively. There are a bunch of alpha and beta applications which will only make it more powerful (for example: DryDock and Harbormaster, which will ease the work for automatic builds: http://www.guywarner.com/2014/05/integrating-jenkins-and-pha...)

In my opinion, Phabricator is one of the most powerful tools around for doing code reviews and effective collaboration management. Even with the large amount of beta applications (which are promising in many cases) the decision for us was easy to make.