If you have TechNet or MSDN you can download Exchange Server 2013 and/or Lync 2013 and these both appeared today.
For those of you who like documentation, you can either download it or view it on the web. Here are the links:
For Exchange Server 2013, you can see a side by side comparison of the major topics has changed between the preview help file and the RTM help file:
In addition to Lync and Exchange 2013, Office 2013, SharePoint 2013, Project 2013 and Visio 2013 have been released as well:
Remember that even though Exchange Server 2013 has been released, interoperability is not supported yet with older versions of Exchange:
“Exchange 2013 can’t be installed in the same Active Directory forest as Exchange 2007 or Exchange 2010. Use an Active Directory forest with no prior installations of Exchange 2007 or Exchange 2010. Coexistence with Exchange 2007 and Exchange 2010 will be available at a later.”