I've not demoed the Metal Muff, nor have I checked out any demos on You Tube, but after looking it up, I may have to check it out. I like that there's an added "top boost".
Two questions.... is the top boost a volume boost so solos can be heard over the rest of the band? Or is it a drive boost to give them a little extra sizzle, like using a tube screamer in front of an overdriven amp?
Also, has anyone checked out the MXR Fullbore, and how does that one measure up against the Metal Muff?
The MXR has huge high-end hiss constantly, it's awful. MM hands down. Although I will say the Top Boost on the MM I don't use at all, since it sounds awful. But it's totally your choice.