Just got news in my inbox that all the US Virtual Labs for both Technet and MSDN are running on Virtual Server 2005 R2 which I thought was kind of cool.
If you haven't had a chance to play with the online labs - you should. There's lots of labs which get regularly refreshed, and more importantly take the stress out of having to build your own virtual environment to learn more about the technology. For example, on the TechNet virtual labs, most technologies are covered including ISA, SQL Server, MBSA, WSUS, Active Directory, SMS, Live Communication Server, RMS... and the list just keeps going. For developers, worth checking the MSDN virtual lab site too.