I finally completed the installation of Vista over VPC a few weeks ago but not without burning midnight oil. First, I tired long and hard to install Vista directly as the guest OS on the VPC but after several long (i really mean long. In one instance, i let the insall run for over 10+ hours) failed attempts, I opted to install XP first on the VPC and followed it by installing Vista. Now I could smell the fruit of my hard work.:)
If you are a MSDN subscriber, beta 1 download is available now.