We use phabricator. It has some really nice features.

* Easily automatic updating.

* Really nice code reviews.

* Many features built in.

It also has some very terrible downsides:

* It expects you to use its work flow (though you can work around it) for merging code back into master.

* It requires manual config per git repository.

* arcanist is a pain to install (and php)

* Its expectations don't seem to quite match up with gits. It seems to often have trouble figuring out what I'm trying to send for code review. I've given up on it being smart and now just always run: `arc diff master` or `arc diff master --update D<ID>`.