It sounds just great, awesome. For any setup for the controls range/position you could try. 4 controls for a simple and still wide options. So versatile!!!
From a smooth and low end growl with the Gain control almost on the minimum, up to the cleanest fuzz for a bass with a bunch of options at both ends of the Tone control.
It really works awesome with other pedals (synth, modulation, everything!), and thanks to the Mix control you can blend it into your sound so accurately.
I have a Spector legend 4 with aguilar soapbars (with OBP-2 preamp) and the Red Muck keeps the essence of the bass, but adds a notorious and still "gentle" punch to the sound. It really gives the bass a entire new range sound coloring.
I couldn't be more happy. Really, really great purchase.