I'm reading vague spoilers here. Good thing I'm headed towards the end of season three (only two and a half more episodes to go).

Still, even with the first seven cylon models being what they are, they are different from each other. Even within a number they are different; Sharon is living proof of that. But even if that wasn't the case, you'd still have seven different models which would make the cylons, well, cylons. You know?