VMWare 4.5

Boot time: 1 min 40 sec.
CPU Usage: 1%
Network: Could not get the adapter drivers installed.
Usage is obviously slower than on a physical machine, but not too bad.

VPC2004

Boot time: 4 min 45 sec.
CPU Usage: 85%
Network: Worked fine.
Usage is so bad that I can see the Start Menu rendering when clicked on.


Conclusion:  If you really want to run Windows Vista Beta 1 in a virtual machine and don't care about the network adapter, I'd go with VMWare byfar.