The beta is now available to manage WS08 R2 Hyper-V and MS Hyper-V Server 2008 R2. Check out RakeshM's blog post. Rakesh is the principal group program manager for SCVMM, and can answer any questions you might have that he doesn't address. If you're looking for brevity, see Larry's post over at the System Center team blog. You can download the beta of Virtual Machine Manager 2008 R2 from the Microsoft Connect site.
On a related note, join Microsoft's sr. technical product manager, Edwin Yuen, in a live web chat on March 31, 8am-noon PST [11am-3pm EST]. Edwin will answer your questions about Hyper-V, SCVMM, App-V, MED-V and other items. See more here.
A reminder also that the Microsoft Management Summit is April 27 – May 1 in Las Vegas.