I've got a triple-black 02 S and I've tried Maguiar's NXT and P21S. Of the two, the P21S looks better IMHO. It's relatively expensive but it goes on like soft butter and comes up just as easily, leaving quite a deep lustre.
If you
really want to do it right, use Klasse All-in-One after washing, then two coats of Klasse Sealant Guard after (letting the first coat sit 8 hours or longer), then the P21S. Go to
http://autopia.org and
www.autopia-carcare.com for the best info on detailing; it's the Mother Lode for such information.
You can get all the products from the Internet, or pick up Klasse products at Mercedes and Porsche dealers (although they jack up the price quite a bit).