I just broke my driveshaft two weeks ago, and bought a Mark Williams. It's a bit pricey but you can really tell the difference in the parts. I got the 3.5" chromoly driveshaft, with their high end yoke. They claim that the 1350 u-joint is stronger material or will not break before the output shaft, probably cause of the length of the output shaft.
I have been using a Chromoly shaft built from M/W parts for a number of years now and never had a failure. We also need to order a new shaft for our new car since I sold the old one with the other car. I would like to use a carbon shaft for the weight but I have seen quite a few failures that caused extensive damage to the car. I think with that being said, I will just order another c/m and be done with it and have a little more piece of mind. I know lots of guys that wouldn't use anything except carbon and others that wouldn't use them if they were giving them away. Like anything else, there is going to be good and bad stories from all of them.