As another alternative to GitHub, we are using GitLab CE on-premises. This is the open-source version and we've been pretty happy with it in a team of 50. And if you want support and some extra features, then the pricing is much more reasonable than GitHub & GitHub Enteprise.
Having used both GitHub and GitLab pretty extensively I could only recommend GitLab if self-hosted and cost are your primary requirements. That being said GitLab is an impressive product given the development forces behind each.
I'll make an effort to take notes over the next few weeks and put something up on the issue tracker. To be absolutely clear I think GitLab is pretty good I'd just prefer and recommend GitHub still if self-hosted and cost weren't the primary requirements.
See: https://about.gitlab.com/