aluminum and carbon fiber driveshafts

I have used aluminum driveshafts in a few of my cars. They are lighter, so less rotating mass means more horsepower makes it to the rear wheels. Carbon fiber ones are usually just a carbon fiber shaft glued to an aluminum or steel end. The carbon fiber shaft is supposed to absorb harmonics better and therefore feel smoother. Is it worth the money? I guess it depends on how the car will be used. A car driven to cruises and shows won't need one but if the car sees any track time it is a good mod.