One feature of vsphere 4 is a game-changer - EVC - enhanced vmotion compatibility. It allows vmware to use new CPU features for virtualization management, but uses lowest-common-denominator features for running operating systems, to enable vmotion between modern Intel cpus, OR modern AMD CPUs, but not between the two. Without this feature, I felt forced to buy more old CPUs. Now I'm free to buy new 6-core CPUs, for example. Once we test the new CPUs, I'll post about it.