I must agree with ozziegn, I want a case that is always on protection (I just bought the Apple case) , but for traveling I could see an advantage.
But I really disagree with Abyssgh0st. I recently received a Dro concepts "Guardian" carbon fiber case as a gift for my iPhone 3gs (I'd never heard of them before this). It is very well made, the gloss finish really nice, and the quality of the carbon fiber work is top notch. I would recommend their iPhone cases to anyone.
Vaja also makes a nice product too. I had one of their cases on my original iPhone.
If I understand correctly, the real pics are from where it just came out of the mold, i.e. raw carbon fiber w/ resin without the glossy clear coat added. It will look a lot better once its sprayed with clear and buffed.