Ubuntu provides virtual images that are used by Amazon EC2. They can be started locally e.g. by running:
qemu -fda precise-server-cloudimg-i386-floppy -hda precise-server-cloudimg-i386.img
Question: are there pros/cons of using these images instead of creating own ones from ISO files?
Getting Started with Ubuntu Enterprise Cloud
Note: Starting with 11.10 (oneiric), Ubuntu Enterprise Cloud is replaced by Ubuntu Cloud Infrastructure, which is based on OpenStack.
You're getting a package of "enterprise grade" management and infrastructure tools. My guess is that they are not installed or included with the traditional installation media. Check it out, see if you need any if it and base your decision on that.