This is the kind of pedals that does one job, and do it right.
It's definitely a leads beast, you'll get some screaming leads out of there - for long sustained violin-like bend (for your inner Gilmour wanabe) or crazy roaring stuff (think J mascis)
- For the price, It's a great pedal with a very subtle relationship between the knobs to craft the sound you really want
- Even with the aforementioned tweaking possibilities, in the end, it's all different sides of the same exact thing. You need to make sure this is the sound you actually want - I would definitely recommend to test it and compare it to other EHX muffs to make sure this one will get you there. If it is what you're looking for, go for it, it's great. But don't believe all those forums that will tell you about how "versatile" it is, because it's not really, it can only be tweaked within its own very niche boundaries.
In general, I wouldn't recommend this pedal if you are looking for a shoegaze wall-of-sound type of thing (it hosts 0 MVB vibe) or for this Jack White sound that a lot of people try to achieve. And it won't quite get you to the Black Keys tone either.
So overall, go buy a big muff, you absolutely need one, but trust your ears, or just take the one that your favorite artist has and don't try to find "the best one overall", there is none as they are all so different and so good at what they do :)
If you're into J Mascis or David Gilmour - get this one and stop looking for fuzz forever.