Great when they're juvies. Lots of action and interest. More 'mbuna' like in behavior when younger. I found them to be much less interesting as adults. I ended up with a few males with territories that push all others into a group midwater. Tank size and numbers can make a difference. I've got about 27 now in a 180. They really could use something twice that size. The bigger they get, the smaller the tank looks. If I had to do over, I'd get them young again, breed them a bit, then move them and start with another young group. Just me.
1. They are a challenge - especially wild fish.
2. They come in many different colours.
3. There tends to be quite a good market for fry, esp. F1s
4. Other than that I'm not sure. I guess people just like them!