Well I've got an Ernie Ball Volume pedal and it works great. Smooth, when it's all the way back it's all the way off, when it's all the way forwards it's very transparant, and I found it could also be used to blend a second amp in too.
See, there's the normal "output" and there's also a "tuner out" that bypasses the volume pot, so this would be the unaltered signal regardless of where you position the rocker. Now if you have that going into a clean amp, then you can fade a dirty amp in with the volume pedal. I found it far mroe subtle than the sort of thigns you get with channel switching, kind of like in "Babe I'm Gonna Leave Ya" when the distorted tele comes in over the accoustic guitar, I didn't even realise at first.
But even if you just buy it for what it's intended for it's a good solid pedal, seems reliable, and it's passive and transparent.