I really like it. I leave it at ~30% up and it doesn't really change the inherent tone, but I use it a lot with single coils to beef them up (when I want a hotter single coil sound), to make a crunch tone just a bit crunchier (it gooses a JCM 800 just a bit, for example), or to make a boosted overdrive tone a little thicker (I find that using an OD pedal as a boost seems to gut some midrange or something, thinning the tone, but stacking the MC401 thickens the tone back up).