The System Center Virtual Machine Manager team is pleased to announce the release to manufacturing of SCVMM 2008 R2. To help you upgrade your existing SCVMM 2008 environment Kerim Hanif, Program Manager SCVMM, has posted a helpful blog for upgrading.
http://blogs.technet.com/chengw/archive/2009/08/24/vmm-2008-r2-upgrade-guide.aspx
System Center Virtual Machine Manager : System Center Virtual Machine Manager 2008 R2 RTM