After listening to a few demos of the Nano Big Muff, I decided to buy one. I must say that while it offers excellent sounding fuzz tones when paired with other pedals, such as an overdrive, The Nano Big Muff sounds disappointingly thin on its own.
The pedal sucks out all the mids from your signal. While this may be preferable to some, I personally dislike how easily this pedal gets lost in a mix. The tone knob doesn't exactly fix the issue. Bringing it down all the way removes all (and I mean ALL) high end from the sound while boosting the low end. On the other hand, bringing the tone all the way up leaves you with nothing but harsh treble, which is very hard on the ears. I prefer to keep my tone around the 12 o'clock mark.
Playing more than 2 notes simultaneously produces a very muddy sound, from which it's impossible to distinguish individual notes. Rolling down the sustain helps with this issue, although it doesn't completely remove it. While I personally have a soft spot for this sound, some may not. Rhythm guitarists beware!
The Muff, like all EHX pedals, is built like a black box from an airplane. The exterior is made of metal and feels very solid. While people seem to have mixed opinions on it, I personally like the loud and clicky footswitch. You really feel when you turn the pedal on (or off).
I know I sound like I dislike the pedal, but like I said, it sounds AMAZING when paired with other pedals. It may not be for everybody, but I do recommend it. If you're a fan of Dinosaur Jr. or Jack White, this pedal is for you!