I just stumbled across Robert McLaws post Microsoft's Virtualization Offerings Suck and I do agree with a few of the points he is making (GUI and 64 bit guest support mainly).
We've been sticking with Virtual Server for some time and the main reason for that has been PSS supportability and licensing (Actually we have both VMWare and Virtual Server in our environment). But now we want to setup Exchange 2007 in "real" production environment and has bought a beefy server for that (Quad-core, 64 bit, 8 GB, six 15.000 RPM spindles in RAID 10).
Furthermore, as we wan't to mirror our enterprise customers environments I was planning on using Virtual Server to create and separate all the possible Exchange Server 2007 roles on a single server.
I've been running the 64 bit version of Virtual Server 2005 SP1 (Beta 2) for a while on my demo machine, but only with 32 bit guests due to the products I'm testing (Primarily LCS 2005 and Exchange 2007 32 bit). I thought that 64 bit guest support would be part of the final SP1 package (never bothered to check 'cause it was "a given"). But I just discovered that its first planned to be released as part of the Windows Server Virtualization (a.k.a. Viridian) offering that is due 90 days after Longhorn release and then only on the Longhorn platform :-(
So I guess we will ditch the support and go with VMWare Server for this server (I guess I for a while will have a hard time to handle customers complaints regarding how they think Microsoft supports "legacy" systems and how the products always seems to be much better/working as they should .. in the "next version").