Exchange DAG and Cluster recommended Updates
My former Microsoft MVP fellow and well-known Microsoft Exchange Cluster Expert, Scott Schnoll, published a new blog post giving a headsup on recommended updates for Windows Failover Cluster environments with Exchange DAG implemented.
It is worth reading his blog post now and prepare for some patching soon.
http://blogs.technet.com/b/exchange/archive/2011/11/20/recommended-windows-hotfix-for-database-availability-groups-running-windows-server-2008-r2.aspx