They are kind of like a nicer, more aggressive Oscar.
They are very hardy and easy to keep, but very messy - love to eat and love to poop. They also rearrange the tank as they see fit. They are certainly among the 'smartest' fish available and quite fun to own. They need a lot of room, and you'll have a hard time keeping more then one in anything less then 100 gallons, I wouldn't keep one in less then 60 or so gallons.