does the AI just share one personality?

What makes the different leaders different from one another? I think that there should be random play styles for the leaders...aggressive, passive and such. Civ IV implemented this quite well. As for custom leaders, I think you should be able to give them a personality from a list of them as their default. All leaders should have a default personality but we could have an option to randomize them. If this has been implemented already I must have missed it somewhere and I am sorry.