I've used my amp distortion (Rivera M60 combo) for ages, and this was the first pedal that I heard and thought "Yeah, that'll do!".
The gain range is good, and there's plenty of volume available. I've used it with two guitars, a strat and a les paul, and though I find both work fine, it would be nice to be able to get more gain from the strat. It goes high alright, but higher would be good. I run a booster into it, which works very well.
I haven't used the internal control for the voltage supply.
The tone knob covers a useful range, and I find I can get a bunch of useful sounds out of it.
I like the tone shift switch as well, though I find it a bit frustrating that there's such a level jump when it's engaged, I'd prefer to be able to switch it on and off without having to reset the volume control.
All in all a nice pedal!