At TechEd, Microsoft announced the key new features that will make it into the Release Candidate of SCVMM 2008 R2 in late May, that weren't in the Beta. Here’s the extra features: Storage Migration, Queuing of Live migrations, Rapid Provisioning, Host compatibility checks, Support for 3rd party CFS, and Support for Veritas Volume Manager.
Storage Migration enables migration of a VM’s storage both within the same host and across hosts while the VM is running with a minimum of downtime. The downtime depends on the amount of activity going on in the VM at the time of migration, our tests have shown typical downtimes to be less than 2 mins.
More info: SCVMM Blog