Thanks for the nice article, quite what I was looking for, as we need some virtualisation at work, and the main war is between vbox and kvm
However I miss some thing, which you can hopefully add/clarify:
1. Was VT enabled in VirtualBox? IIRC 2.1.4 doesn't do this by default. If it wasn't - would you rerun the tests where VirtualBox was *really* bad compared to the others?