I have two Muzzy carbon Mag arrows. I bought 'em back when they were 22.00 each. (which is still pretty ridiculous for a fish arrow)
They don't weigh any less than a standard fiberglass arrow. They are straighter and take a bit more abuse than a regular white 'glass arrow. (a nice thing if you don't lose many arrows)
I did shoot the one so much (into rocks) that it actually cracked all away around near the point. It was still strong, it just looked freaky. I did end up cutting it down. I heard that Muzzy would replace it, but I didn't bother. I figured it was my own fault for missing carp and hitting rocks.
So, I recommend them if you don't lose many arrows and want a tough, straight arrow and have extra cash burning a hole in your pocket.