I would describe the sound as something between a fuzz and a distortion. It's insanely loud, has a ton of low end, huge wall of distortion, but it's somehow still tight enough so that you can do palm-muted stuff with it. This is where most fuzz pedals fall short IMO.
I use this in my doom/stoner metal project, and IMHO it fits there just perfectly! I would imagine that for less extreme styles this pedal is too much.
I like how well the pedal responds to my amps EQ settings and the guitar's volume control or a volume pedal. The pedal only has one knob, but it works so well with amp and guitar controls that you can color the character of the drive really using those. Dial back the volume using your guitar's controls or a volume pedal, and you get a more mellow overdrive. Change the tone using the EQ on the amp etc.
Only con I can find is that there is generally a really narrow area in the one control knob, where the sound is usable. The minimum setting sounds garbage and maxed out it's just fart sounds.