Do you use any particular automated provisioning service that tries to match your computing demands such as Novell's Platespin, or just make manual copies of a "golden" VM image when you need to bring up a new server? Please feel free to share what you have used that works for you (or doesn't).
There are various products that can do this, including vMotion and others from VMware and PlateSpin from Novell. The trick is doing the provisioning automatically, so you don't have to monitor the demands on your servers or worry that you have too much or too little horsepower in the cloud and pay for things accordingly.
I've read this thread and am very interested in the result but unfortunately I don't have an answer for you. I'm just starting in the world of business IT or else I'd be more than happy to help. I hope someone more knowledgable gets an answer for you!