I'm not sure I'd be too quick to warn people away from all butterflyfish. I have a 3-inch Raccoon Butterflyfish
right now in a fairly young tank (2 months, I believe, when I added him) and he's a happy-looking, active fish that gets his share during feeding time. I just have to make sure I put in bits of frozen food small enough for him, but brine shrimp, spirulina-enhanced brine, and mysis all work. Never used live food. He comes right to the surface without fail.
Of course, it's possible that the addition of my three longfin bannerfish, which are related to the butterflies and are supposedly hardy, had something to do with it; he often hangs around them and they are very active fish and very enthusiastic eaters. I put those in right after the Raccoon.
Anyhow, I'll change my assessment if I run into any problems down the road, but so far I've got a good opinion of the bannerfish and Raccoon.