[Delphinus]

Wow, and I thought I've had bad luck.

I don't know how else to respond to that, Reef_Raf. I have all of the above and nowhere near those kind of problems. Now with that said, I do have a mistrust of anything that has claws, shrimp or crab, generally speaking. When you get down to it, none of them are "nice" and restrict themselves to only algae. But every animal has an impact: for some I choose to take the good with the bad. Hermits are still awesome janitors cleaning up leftover food and whatnot. ... In my 50g I have three fish, several dozen hermits, several dozen snails, two cleaner shrimp, one peppermint shrimp, and several thousand brittle stars, several thousand worms, and countless pods of various shapes forms and sizes. The only real downside to the crustaceans, I have found, is that I can't beat the shrimp away from my open brain when I am trying to feed it. I have to sit there and wait while it eats and shoo them away until the food is gone, which takes usually a good half-hour. And I admit that this process gets old real quick ... but ... I don't think I'd ever get rid of the shrimp. There are reasons they're in the tank, and they fulfil those reasons. If for nothing else, they spawn like nuts and I have a good steady supply of planktonic food for everyone else. But the whatever the effects ... If I didn't want them I wouldn't have them. They are a purdy thing to look at and people come over and say "oooh neat."
I think it depends on what your goals are. If a person's intent is to have a minimally bioloaded SPS tank, then yeah, stay away from the fish and the crustaceans. But in a mixed tank, different bag of tricks.

As you say, maybe the thing to do is try it, and then see how it goes. If it works out then great, if not, then regroup.

cheers :D