I've got two huge ones, and one smaller one. The large ones I've had for close to 3 years. While they definetly rule the tank, they aren't agressive generally and in the past have even ignored several smaller chiclids they could have easily consumed in one swallow.
Probably the funniest thing about Parrots is that they constantly try to mate. Its kind of sad in a way, they lay eggs every couple of weeks or so, but my understanding is that because they are a crossbread they are completely sterile.