Today we released an update to the Hyper-V BPA (Best Practice Analyser). This fixes some issues in the previous BPA and also correctly handles the new Dynamic Memory and RemoteFX features in SP1. No new rules have been added. To install the update, you must already have the Hyper-V BPA installed (http://support.microsoft.com/kb/977238). Note that both the original BPA and this update apply to Windows Server 2008 R2 and Microsoft Hyper-V Server 2008 R2.
While I recommend you have SP1 installed, this update also applies to R2 RTM Hyper-V. A quick summary of the fixes:
http://support.microsoft.com/kb/2485986 is the place for all the information on the changes and the download link.