I have those on my 01 Boxster S, 285/30-18 rear and 255/35-18 front, love them.
They are not quite as sticky as a StarSpec or RS-3 but still good for decent lap times.
What's amazing about the S-04 -s the wet grip, even when it's pretty cold, they work well done to 40F. Other comparable tires usually get scary in the rain once its below 55F or so (I live in the Seattle area, cold wet grip is VERY important here..
