We have just released Mono 3.0.4 to the world.
The release packs our SGen concurrent collector with a new strategy to deal with pinned objects called cementing (Mark discussed that last year). We are very excited about this new feature.
MacOS users will be happy to know that we no longer install a /usr/bin/pkg-config, so it will not break their homebrew installations and it only contains the new Gtk+ stack that allows the new Xamarin Studio to run on OSX with 3.0.