Half the point behind those clusters is that they can use very low end machines. Have you seen the specs of what Longhorn is projecting as it's system requirements?
It's bad enough having one desktop crash in the middle of my work anyway. I dread the day I get the the call...
Help Desk: The data center's down.
Me: What server in the data center?
Help Desk: The data center's down.
Me: Doh! Guess I'll have to reboot the data center...