Butch is one of Dr. Z's older friends and was one his first adopters back in the very first few years of the business. He says he loves big amps and wishes he had more opportunities to play them.
So he plugged in and started with the Z-80's master volume all the way up and said "that is the best clean tone I've heard, but no one would let me get away with that on stage."
So I said "Butch, play, then tell me when it's comfortable volume-wise." I slowly rolled back to about 11:30 and he said "what did you do? sounds even better!"
More here: http://drzamps.com/product/z-80/