I JUST got done playing on it for quite a while with my Fender Blues Jr. and the results are in...
This thing is brutal! I haven't played Metal/Hardcore music in a long time, and still don't, but this thing can get as heavy as I have any desire to be... I've got my Voodoo labs sparkle drive in front of it (another pedal I love) and if I hit that AND the Lava Box there's the crushing distortion. Without the OD pedal the Lava box is still capable of getting me exactly the rock tones I want for when I'm jamming out of Sabbath/KISS/Neil Young songs, and it gets every bit as heavy as I want it too. Definitely a good investment!