I've got two pieces of a 30%carbon matrix 2000 460 from a friend - it snapped just below the ferrule (flash word for the bit where the top section slides over the bottom section) while he was downhauling it in the carpark. NP replaced it for him, and the replacement went bang in much the same way, only on the water while being sailed (not crashed, or jumped or anything!).
That said, I have two NP 30% 430's and haven't seen any problems yet. I believe that NP had a bad run on masts for a while - hopefully they got that sorted quickly seeing as NP sails only set properly on NP masts!
On the other hand, I have a Tushingham 430 that is covered in microscopic carbon splinters.. Ouch!

Apparently that's due to over use, and a combination of water penetration and UV deterioration of the outer resin..