I also highly recommend Phabricator - it has excellent tools, active (paid) developers who are excellent people, and is very easy to maintain and use. I also think it simply scales to bigger projects much more effectively than GitHub (in some important ways - like emphasizing rebase and small, continuous development, a better UI, and better notification and commenting/review system as well). That's just me, though.

We use it for GHC, and I've had bugs fixed within 10 minutes of finding them on our live install thanks to the devs. They've also helped us write extensions and customize our Phab install. We've had a very good experience all around.

Definitely want to check this out. Did they redo their site post F8? I had talked w/ some FB devs at the react conference and one said that the code review process at FB was the #1 thing that made him a better programmer day in day out.

Cool suggestion, I will give it a try. Great that it works with existing repos.