I thought I'd chime in since I've had recent experience with a Humu Humu (aka, Picasso) Trigger.
I have a 90 gallon tank, with a crap load of live rock, some corals, and a few fish (Yellow Tang, Blue Tang, Tomato Clowns, Chromis').
One of my friends shut down his tank a month ago and gave me his Trigger. It was two inches long when I got it. I loved it because it was so active and had a personallity. However, I quickly came to realize that it was not the best of tank mates for my other fish. Not only was it a very aggressive and messy eater, it was mean! He would chase fish away from food. Whenever he thought somefish was looking at him the wrong way, he chased them. The Trigger fish also loves invertebrates, especially hermit crabs. That one Trigger took my Hermit crab population down to about 20 from an original 50 or so. Trigger's have teeth (or a beak), so they can do some major damage. A week ago I noticed a notch in my blue tang's rear fin. The day after, I witnessed the Trigger put a second notch in his fin. Anyways, that was the last straw. With great difficulty, I netted him and traded him in for a Flame Angel. He grew to be 4 inches by the time I sold him two days ago.
That was my experience. I guess that was my own dumb fault for thinking I could turn this fish into a community fish.