I have one of these fish in a semiagressive 210g tank. Even the more aggressive inhabitants like him (like puffers and trigger).
As for being difficult to keep, I have read that this is true. The main reason is that they die from malnutrition. Most of them won't eat prepared foods and don't have enough fish in the tank to keep themselves fed through "cleaning". I have been lucky and he eats prepared food.
My cleaner is quite enjoyable. When I have my arm in the tank to do maintenance he actually will clean MY hand and arm. He seems quite fearless in this regard, and also with the fish. I have heard that they can be kept in even very aggressive tanks due to the fact that their coloration and markings make them recognizable to fish as a beneficial aid.
I'm not sure about them being reef safe, as my tank is a FOWLR
tank, but considering they are strictly carnivores, I think the chances are good that they will leave the anemones and corals alone.