Yes they are carbon wheels with centres made from magnesium/aluminium (magnelium). Old ones were with magnesium only centres but were prone to leaking sometimes. Main advantage is that they are super light (around 7.5kgs) with most of the weight distibution being in the centre (carbon weighs very little) which makes them effectively even lighter.

Carbon is very strong, just accidentally banged mine on the way out of the garage and and saw its resilience first hand. Have tracked them going over curbs etc and no problem what-so-ever. The improvement on a heavy car like the turbo is really very noticeable. In terms of looks, well lets say that they draw a lot of attention.. (pictures cant really do them justice as the carbon looks very impressive up close).

IMG00034-20081018-1355.jpg