i brought it up on a local board, and a pretty knowledgable DSM guy said that people hate on them without reason. this is just what someone else said..maybe the DSM kits are better??
I have a set of their headers and Y-pipe on a Tundra and they work well. Haven't really had any trouble with them. I can't speak for any of their other products though. Probably not a company I'd buy a lot of high dollar parts from, but I don't really have anything bad to say about them either.