If you are running Windows Server x64 and using Hyper-V most likely you still have beta or RC0. You can now downlaod RC1 http://www.microsoft.com/downloads/details.aspx?FamilyId=7EDAA89F-9F64-488D-93C0-858D2D8799DF&displaylang=en for x64 systems.

The virtual network configurations and virtual machine configurations are compatible and are migrated in-place. Make sure to read the KB at http://support.microsoft.com/kb/950049. Saved states and snapshots are not supported in this upgrade :(  but hey, that is the price you pay for being in IT. So get the download and have some fun!