It includes all the errata and security updates, which have been released so far. The Ubuntu mirror has also been updated.
The corresponding release notes can be found at: http://download.univention.de/doc/release-notes-ucc-1.0-rev3.pdf
Further information on the new UCC update can be found in the Univention forum at: http://forum.univention.de/viewtopic.php?f=54&t=3086/