I am in the process of switching my demo laptop over to Hyper-V to see if I can't get some better performance from Virtual Machines than we currently get with Virtual PC. In the mean time the Virtual PC team has released Service Pack 1 for VPC 2007. It is available in 64 and 32 bit versions. If you are running VPC, this is worth your time.
Download details: VPC 2007 SP1