I wanted to check on some of my opinions I stated above and I did talk to a few people that have kept them for 2+ years. I think long term success with this fish is possible. I wish more people that kept them for 2+ years would post on boards so I could learn what I am doing wrong.
As for info on what I have observed them pick at or eat or kill is the following.
The one I have now started as 2. The pair did well (eating) for a month and then the smaller of the 2 would chase/bite and stress out the larger one to the point that it ended up passing. There was another issue with it swimming erratically. These 2 fish were a rescue of sorts so I did the best I could with my limited knowledge.
I have also observed them eat/pick at snails. I think mine has a kill count of 3 in 4 months. He has also killed a Emerald crab.. Picked off all of its legs.....
As for shrimp and other fish it does attack a Kole tang and sexy shrimp.. It does not seem to want to eat the shrimp just wants them to move where he thinks they should be I guess.
As for coral I am sure at this point he has picked at every coral and anemone in my tank. Killing/eating doughnut corals (including the one in my profile pic), zoanthids, acan's, duncan's, pipe organ. Out of the ones I have kept they all seem to do the same thing within 3-6 month. I have also found they seem to stick to brown or green coral. I kept a colony of rainbow acan's in my tank for 2 months and the one I have now never touched it. I have also noticed he stays away from the bright colour zoanthids. Seems to nip at all the brown ones.
Other then that I have also found they don't QT that well. This could be me but I just hypo them no copper as everyone I have used copper on seems not to last.
I hope this helps and to be honnest this is all just anecdotal information.