So far so good with Eucalyptus. I like the base system and can now move images back and forth between Amazon and my local Eucalyptus deployment. Works quite well - the only real limit is my bandwidth. That will resolve itself with FIOS in a few weeks.
The best interface for managing Eucalyptus that I have found is Hybridfox. It's a re-roll of Elasticfox that supports EC2 and Eucalyptus from the same plugin. Unfortunately S3Fox doesn't seem to extend to Eucalyptus. The best I have managed so far for a Walrus (Eucalyptus S3) interface is an older re-rolled version of s3cmd. It's workable, but not even in the same ballpark as S3Fox for ease of use.
I also chimed in on one of the Eucalyptus forums with a few details on migrating images back and forth between Amazon and EC2. They do need to be re-rolled with a different encryption key which may not be obvious.