I love them too. I got three, lost one, leaving a male and a female. I now have maybe six, and the female is full of eggs again.
I have 'em in a tank with some small fish, who definitely snack on the babies. I understand they have a hundred or more at a time, so the fish are obviously snacking frequently. It's nice-I don't want an actual crayfish farm, but a few more is nice!
Behaviorwise, they leave fish, shrimp and snails alone, but do fight if they meet up with one another.