Installed it yesterday without any problems.  Of course, you can't install directly from the ISO, since it's over the 2.2GB limit that VPC has.  I used Alcohol 120%'s virtual drive and mounted it there, then captured this virtual drive in my virtual machine as a physical drive!

Installed in about 2 hours.  Unfortunately, the Vista Beta2 VM Additions don't seem to add much functionality.  Not too surprising since the VM Additions hook into the OS.