Depends what I'm playing, but generally I use them a fair bit (single coils and humbuckers) same as I use the volumes a lot.
What I'd be interested to know is how folks, especially the tone/vol users, set their amps?
I treat all amps (and patches on modellors) as single channel amps, never got on with clean/dirty switching.
I set the amp for my main crunch rhythm sound with the guitar volume on 7 or 8 and the guitar tone on about 6 (unless it's a really vicious tone control! :lol:).
That means I can turn the volume up for "more" or down for "less" and cleaner.
I can also turn the tone up for "more", AND for cleaner, especially when combined with the volume going down (or picking lighter).
I tend to use all this stuff as part of the "playing of the instrument", same as choosing to use pick or fingers, where to pick (distance from bridge), how hard to dig in, etc, etc... I find it all valuable for expression in my stuff, and besides... many years ago I thought "f*ck it, it's there, might as well see what it does" - and because it seemed so useful, I kind of stuck at learning how to make it work for me... so now I'm kind of stuck with using it now!
Anyway, I was just thinking, I wouldn't be able to do this, and therefore wouldn't be using the vol/tone on the guitar so much, if I set my amp up with everything turned up to 10 on the guitar.