I had a pair about a year ago that got along with one another rather well. I ended up losing the male to some sort of intestinal blockage (at least that is all I can figure out). My female now lives in a community setting and is on the aggressive side, but not a killer.
I recently picked up 6 2" juveniles that I am growing out in a 40 breeder for now. They do a lot of chasing with one another, but have not done any real damage.
This is just my experience. I've heard from others that experiences range from rather mellow to psycho killers. I'm going to go with lower temperatures and lots of water movement to try and curb aggression. I've got high hopes, as a friend of mine recently had success getting his pair to spawn.
Good luck with them.