^ yeah. it'll presumably take a lot of the power tube distortion out, but I guess it wouldn't take the preamp overdrive out.
i guess it depends how much gain your distorted sound has. you can definitely get from a rock overdrive/distortion down to clean solely by using your guitar's volume (especially if there's some power amp dirt in that rock overdrive)- perhaps not from a metal overdrive, though.
I guess if you footswitched the gain boost out, AND rolled down your guitar volume, it might do it- but you'd need to get tom to try it on his, first.