For me, the major plus is it looks cool. It has a translucent quality that adds a jewel like quality to the knife handle. If the scale finish is textured from bead blasting, or some other method, it aids in the "grip ability" of the knife handle.
It's also light, but in the amounts used for knife scales, that advantage is barely noticeable.
For sheer function, I'd probably stick with G10 or micarta. But for looks, I'd go with carbon fiber.