Native Perfomance is here today...
In Linux it's called Containers and a package called OpenVZ has been about for a while and the newer LXC is becoming quite popular now. The down-side? Just one kernel running all those containers rather than a hypervisor running individual "PCs" each with their own kernels - that means you can't run 2 different OSs, although with care you can run 2 different Linux distributions as long as they're both happy with the same kernel.
This technique isn't new either - Solaris and FreeBSD have had similar features for a long time and LXC for Linux while part of the stable kernel isn't perfect yet, but it's good enough for me to use in production in the data centre. 100% native performance in each container with none of this virtualisation wastage.