My experience? Aweful. Their documentation isn't the easiest to follow and the interface isn't the easiest to use either. I ended up switching to CloudMin, which now has a free GPL version as well.
Me too, i have a bad experience with Eucalyptus because of the bad docs, also i have noticed that it a bloated software (Java)
i have switched to ConVirt [1], it not cloud management but it's a good software to manage a lot of hosts servers runing VM (both KVM and Xen).
HTH
[1] http://www.convirture.com/