DCD,
I only know of one person using the ATS triple(metal) and he can't speak highly of them enough. Unlike most multi plate clutches you can slip the clutch and the secret is supposed to be in the friction materials used. His car is not driven daily but the wear is excellent considering the power he is pushing through it.
Carbon one is twice as more expensive, therefore i never had it as an option and don't know how they differ from the metal ones.
ATS, ORC and OS are the best clutches available and they all manufacture their own parts unlike Nismo, HKS, Apexi etc... They are also chosen by all the high hp gtr's which may force you think they are a pig to drive. I certainly thought that way till i've been told by many people that, that description is best deserved by HKS and Apexi.