The video is a bit old, it is from November 2008. But it is still quite interesting to see and discuss about it. With KVM you can upgrade your farm of servers easy, it does not matter if the new servers have CPUs with new features or not. I’m not sure if you can do this with ESX, I guess not, you probably need to migrate them shut down.
httpvh://www.youtube.com/watch?v=EuhU6jJjpAQ
Have fun!