I've had one in my tank for about a month and a half. She's one of my favorite fish -- very active and beautiful. I did a lot of research before buying one, and most people report that they are peaceful. I have to say that mine is not what I would consider peaceful, though. Immediately upon introducing her to my main tank, she challenged my tomini bristletooth tang for supremacy (I watched the whole thing -- she was definitely the instig
ator). She very quickly lost that battle and was chased by the tang mercilessly for about two weeks. I introduced a pair of lineatus fairy wrasses to the tank after her, and she was an absolute terror to them for the first two days until they settled in. Now the male lineatus chases her from time to time, but she still occasionally goes after the female wrasse. I think her bark is much worse than her bite. She likes to try to intimidate my clownfish pair and my female lineatus by flaring her fins and "sidling" up next to them, but they usually just ignore her. She doesn't nip fins -- it's mostly just posturing. Fortunately, I'm not adding any other fish to my tank, but if I were, I would definitely be concerned about adding a more delicate fish (like a firefish, for example).
In terms of diet, she was actually kind of finicky in my quarantine tank and would only eat flake food. She wouldn't touch any frozen food I tried to give her (mysis, cyclopeeze, formula 1, etc.). Now, though, she eats pretty much everything.