I've had the M&M's on my car for a few years now and love them. I have to say the main thing that sold me on them was Matt himself. I was having the engine rebuilt under warranty and when the engine came back Arrow, the shop noticed the stock manifolds were cracked (VERY common, at least on Gen III's). I had to get a set of headers quickly, but I had already been reading up on them and was leaning towards M&M anyway.
Anyway, I called Matt to see what he had available and you could just tell from talking to him on the phone that he was a straight shooter and a great person to work with. He said he had a set that he would ship that day and send me a tracking number. When I didn't get a tracking number that night, I was worried and planned on calling in the morning. I didn't even get a chance to call before he called me (no, I didn't have to track down a Viper parts vendor to find out what was going on). He said when he was about ship them, he noticed a small dent on one of the tubes. He didn't want to send them to me like that, so he personally stayed late the previous night and welded a new tube in place, so he could get it coated the next morning. He knew I was in a time crunch with the shop, so he then shipped them NDA and no extra charge to me!
I know you're asking quality and performance opinions, and I've never had the BB headers before, but Matt & MM have the best customer service I've come across in the Viper world and I love the sound and performance of them on my car.