Carbon fiber offers the potential for a higher strength to weigh ratio than virtually any other material. This is at the heart of it's use in the pro peloton. If bike weight is your driving issue (can you feel the difference between carrying one versus two water bottles?), carbon fiber is the answer.
Carbon fiber can also be formed into a number of shapes beyond round tubes. As such it can offer a very contemporary look that steel doesn't offer. Beyond this, carbon looks very special with just a clear coat finish, whether the fiber is a cosmetic woven fabric layer or a random scrim of fibers - nothing else looks like it.
For carbon tubing, I turn to Edge Composites who make carbon fiber tubes to my specification in Utah. Money can be saved by purchasing from the far east, but I won't compromise my standards just to save money. So Edge Composites are who I specify when I select Carbon Fiber tubes.
To my frames I select forks from Edge Composites, Reynolds, True Temper, Easton, or Dedacciai. This gives me a range of flexs and rake rakes to tune handling and ride as desired.