The setup of the Boss HM-2 is quick and it is easy to edit the sound to get a few different sound from it. The parameters you can control are level, distortion, color mix high and color mix low. The high and low are basically tone or EQ knobs and are good to use after you have set your level and distortion. Since I bought this pedal used, I don't have a manual for it and I don't know how helpful it is or not. However, the pedal is easy enough to use that I never needed a manual.
The sound quality from this pedal pretty good, but is limited in its use. By this I mean it is probably only suitable for metal music, and that is what it is intended for, hence the name "heavy metal." Because of the name this pedal will attract the right users as it will work best for this type of music. Since I don't play too much heavy metal, I was hoping this could also sound good as just a general thick distortion. While it works to some degree on this, you can find better options when play other types of music like indie rock.
I've been using the Boss Heavy Metal HM-2 for about three years. I acquired it from a friend and thought it would be helpful to have another color in my set up. While I found it useful in some situations, it isn't too versatile and you can only really get one good sound from it. While it is good at what it does, I look for more versatility when I buy guitar pedals. If you can find one used, you can get one of these really cheap. I don't know how these would compare to the modern Boss Metal Zone series pedals, but I can imagine that they have more versatility and a better overall tone quality. For those interested in playing metal, this pedal is worth a look, but probably won't blow anyone away.