Your Opinions/Experiences with Damsels

I have recently set up my first marine aquarium. It is going quite
well so far, (save a slight red slime problem i am trying to control).
I have put just one fish so far, a small yellowtail damsel. I would
like this to become a reef tank, and i did use the damsel knowing it
was very hardy and would assist in cycling the tank. I have been told
by the local fish store they can be quite agressive despite their
smallish size. What are your experiences and opinions about their
compatability in a reef tank and with other fish, and have you found
them not to be suited to this? Also, have you found any difficulties
in maintaining them with invertibrates, especially small hermit crabs
and cleaner shrimp?

Thanks for your input.

kevin