Just shows "Release" with nothing after it in the "About this computer" view. Test with the fedora-release-12-1 from koji.
Turns out this is because gnome-system-monitor uses lsb_release to figure out the release. This would mean dragging in redhat-lsb for every install, yuk. mclasen says he's going to fix this.
Fixed in gnome-system-monitor-2.28.0-3
Tagged for release.