I said undecided, because I really haven't decided yet
I am playing a CB 1.0 game as Disposable Society, and have decided that once you hit a certain size and economic efficiency threshold, Disposables can be unstoppable; the only problem is getting to that point, especially if other players have the same opinion
I have played CB 1.5 games as Berzerkers, Efficient Workers, Preservationists, and Neutral, and I think that Neutral is a good choice for all-around balance, Berzerkers is best for quick knock-outs and expansion, and Efficient Workers and Preservationists are best for long-haul games, but are a bit slow to start (problem I found with Efficient Workers is, in the early game, you're producing far more than you can use, and thus waste your economic advantage, while some of the other cultures can begin using their advantages immediately).
--edit: brain switched Pacifists/Preservationists... bad brain.