The official announcement of CU1 is here, but the cool thing about CU1 is that it is a full set of install bits, not just an update you apply to Exchange 2013 once its installed. If you’ve been waiting on Exchange 2013, now is the time to deploy and since CU1 contains the full installation of Exchange 2013, your install experience will be fast and complete!
While the Exchange team is releasing cumulative updates as full installations going forward, security updates will still be released individually (and included in the next CU) so that security updates can be deployed in a timely manner.
Until next time,
The release notes say you can't deploy Exchange 2013 into the same forest as your existing Exchange 2010 installation. Is this still a real requirement?