Sound — 8
I used a B.C. Rich Mockingbird (newer 4-knob model) through a 15W Crate Palomino 1x12 (tube) and then again with a Jackson Randy Rhoads Flying V through a Mesa-Boogie Roadster Half stack (tube. as if you didn't know). Through both guitars and amps I was able to get a great distortion sound from the pedal. While the distortion is powerful and you can produce an awesome grind with it, it's very limited to it's task. Unless your into bands like Ozzy Osbourne, White Zombie, Metallica or other metal bands then you may want to consider a different pedal. Other than that I'd have to say it's the best Boss metal distortion pedal you can buy (especially after the fiasco that was the MT-2 metal zone).
Overall Impression — 9
This is (in my opinion) the best distortion pedal designed to play metal that Boss has made. It's heavy, easy to use, and can go from growling bassy distortion to head ripping high tones. It is limited in the range of sounds but for any type of metal it wont let you down. Just be warned that it does get weaker in sound through a Solid State amp than through a tube amp.
Reliability & Durability — 10
Like any Boss pedal this one is built like a tank. Its battery life is pretty standard for a pedal (4-6 hours continuous playing) but a power supply would be better in the case of a gig. Don't expect the casing or pedal lever to break on this stomp box. It can take quite a bit of abuse and is definitely gig-worthy.
Ease of Use — 9
Like any good Boss pedal the controls for this one were simple: It has 4 swivel knobs (the modern looking ones that attach directly to the surface of the control panel on the casing) One level, low, high, and distortion amount. I found it very easy to coax whatever sound I wanted out of this pedal as it's low and high knobs were fairly responsive (no large spots where the tone wont change). The pedal part of the box wasn't jammed or too stiff to easily activate it on command; the springs were fine as well.