I’ve talked about, presented about, and written about this topic quite a bit. There’s already a TechNet article on the topic, but Microsoft has also issued a document called Best Practices for Virtualizing Exchange Server 2010 with Windows Server 2008 R2 Hyper V.
“The purpose of this paper is to provide guidance and best practices for deploying Microsoft Exchange Server 2010 in a virtualized environment with Windows Server 2008 R2 Hyper V technology. This paper has been carefully composed to be relevant to organizations of any size”.