Capt. this may be the wrong forum, this
one is mainly oriented toward production boats. You will find excellent and dedicated racing enthusiasts in this group but mostly amatuers, sailing off the shelf rigs. They would probably confirm that first should come sails, halyards, instruments, bottom treatments before considering mast replacement. The weight aloof reduction should not be that significant. On the other hand the gained stiffnes will probably allow more transfer of power. You ask if they are worth it; obviously to the racing boat builders and proffesional competitors they are but the average weekend warrior may find better uses for their racing kitty. One of the most succesful uses of carbon fiber is in racing bicycle frames and components, it allows for lightness in weight and strenth. A bicyclist has to carry the weight of the machine for hours in a road race so weight becomes an important factor. Also the increased stiffnes translates into better acceleration. Luckily in sailing our bodies don't have to carry the weight of the mast. Composite carbon fiber golf club shafts have been popular for years but interstingly very few tour pros use them. They claim they do not get the same feel of the club head. Ultimately the price, one of these masts may cost more than your boat. I cannot comment in durability, ease of repairs, and other incidental factors.