I have one on my DC2, it constantly gets mentioned that it's no louder than OEM out of VTEC but I think it is, personally. It's quite 'boomy' but some people like that, I personally don't mind it. Once in VTEC it makes a fantastic noise, and not too loud. I can't comment on it's restrictions, I'm not even sure on it's specs B-pipe wise. But I know it's mild steel up to the backbox where it becomes stainless. So it's got a limited life span.
I've got a twinloop to go on it when it's next on the ramps but I'll probably keep the Dragger it in the cupbaord as it's not worth much and it allows me to go back if I don't take to the Mugen. It's also got a massive tail pipe (you can throw a large citruis fruit up it from 10 yards).