Well, I've read that they are one of the more peaceful cichlids, and actually should not be mixed with more aggressive fish. But, then I vaguely recall reading on here that you have to be careful with them because they can be aggressive. I know that when breeding they will aggressively protect their babies, but otherwise I think that they are generally ok. You want to be careful with male to female ratios, as they pair off. If you end up with a pair and a loner I think it might not go well for the loner. They can also be hard to keep alive, and need high water quality. I have 2 at the moment, I think both males, one significantly larger than the other, and they are both fine in my 55 gallon with platys, danios, cardinal tetras, clown loaches and a clown pleco. They occasionally chase a bit when I put a treat in, but otherwise they are fine, both with each other and the other tankmates. I did have a few die before ending up with these 2. Most didn't last for more than about 3 days, and the last one had been gasping at the bottom for a few days and I finally euthanized her. So, if you can get a healthy fish and keep it alive, I think they are great. The larger one that I've had for a few weeks is actually one of the most friendly fish in the tank towards me. When I approach the tank he often comes over to check me out, and will swim up to my finger when I place it on the glass. He also ate some of a zucchini slice out of my hand. I love them both. Very colorful, friendly and active, but it's hit and miss finding ones that survive. Probably more than you wanted to know, but there's my input. Also, here's a link to a profile.
Ram Cichlid Profile, with care, maintenance requirements and breeding information for your tropical fish
And here's the one from this site:
http://www.myfishtank.net/reviews/showproduct.php/product/95/sort/7/cat/5/page/1