I have used VPC 2004, and now I have Virtual Server 2005 installed on my second machine, and I have server images set up with all my different environments.  I’m installing Yukon right now.  I found it interesting that vServer 2005 uses the VNC standard for it’s remote server control.  This was a bit of a nuisance since I use RealVNC on the server anyway.  Virtual Server wanted to use port 5900, and RealVNC was already using it.  I configured vServer to use 5901, but apparently there is more than one configuration point because that broke the configuration page.  I ended up having to configure RealVNC to use a different port so vServer could function properly.  I love VPC 2004, and vServer enables me to use virtual PCs on a remote computer, so as long as I have the disk space, I can set up many different server environments.  It’s a great product.  The hard drive files are compatible between VPC and vServer, but the .vmc configuration files are not.   No biggie.  The hard disk file is what matters, so you can take an image on the road with your laptop by using VPC.