Warning: Exchange 2010 does not run on Windows Server 2012 when this article was first written, but will be engineered to do so.
Running Exchange 2010 DAGs always meant installing Windows Server 2008/R2 ENTERPRISE Edition, as DAGs require the clustering components that are not found in Windows Server 2008/R2 Standard Edition. Enterprise Edition is considerably more expensive than Standard Edition. It also allows much more RAM, as Windows Server 2008R2 Standard Edition is limited to 32 gb.
However, Windows Server 2012 Standard Edition includes unlimited memory and all the components previously reserved for Enterprise Edition. That means that a DAG running on Windows Server 2012 will be significantly cheaper than a DAG running on Server 2008/R2.
