DAG support in E2010 Standard Edition
Today has been announced that the new DAG (Database Availibility Group) feature will also be supported on the Standard Edition of the new Exchange 2010 product.
Since the Standard version only supports up to 5 databases (compared to 100 db's for the Enterprise edition) this will be especially useful for the smaller corporations.
DAG still uses components from Windows Clustering, therefore the OS still needs to be Windows Server 2008 Enterprise Edition.