I have one... when I come back from vacation I'll buy more. I keep them with Rainbows, clown loaches and eartheaters in a 60g.
Mine didn't eat for the the first 5 or 6 days... the rainbows kind of pushed him around.... now he eats.... and pushes the rainbows around. He likes to grab a pellet or flake and spit out and then eat the smaller pieces.
I have been advised to keep them singly or in groups. Don't know the accuracy of that statement though. Others here have said otherwise.
My pH is 7.7 and medium hardness. I keep the tank at 76 degrees and let the warm weather take it wherever it wants. It rarely goes over 84. Some shops keep them under acidic and soft conditions. Check with the store before you buy. (as you do with every purchase, right?)
I love them! Given that you'll have the fish for years and years (like most fish, right?) 30 - 40 dollars is not that much. And they are certainly more entertaining than discus. I particularly like the green sheen on the top portion of their body offset by fabulous markings on their scissorlike tail. The classic red and black racing stripes off a 60s era Ferrari doesn't hurt either.