Please check it out and let us know of any bugs you find. The regular fedmsg topics documentation shows examples of just what kinds of messages get rebroadcasted, so you can read all about that there if you like. The site has a neat dashboard that let's you toggle all of your various repos on and off -- you have control over which of your projects get published and which don't.
I know there's concern out there about building any kind of dependency between our infrastructure and proprietary stacks like GitHub, Inc. This new GitHub integration was a quick-win because we could do it 1) securely, (unlike with transifex), 2) with a low-maintenance, self-service dashboard, and 3) lots of our upstreams are on github or have mirrors on github. If you have another message source out there that you'd like to bridge in, drop into #fedora-apps and let me know. We'll see if we can figure something out that will work.