I fell further in love with EC2 today. I needed to set up a quick and dirty web cluster to test some stuff out (working, as I do, for a distributed computing company) and I didn't have any spare machines at my disposal. Not to fret, I thought to myself... EC2 to the rescue.
In minutes (in between meetings), I had a machine up and running. I installed the software I needed (Java, Tomcat, Terracotta, etc.). In a few more minutes (a little later in the day, between two other meetings), I baked that instance out as a machine image and deployed it on three separate instances.
In less than an hour's work, I had a three-machine web cluster up and running, serving pages over the Internet, and ready for my testing. Even better, I can continually bake out the state of my cluster and publish those images so other people can run the same test themselves.
It's astounding how easy it is to set up a complex computing environment with EC2.