The distortion can get pretty dirty, but that is by my pretty dainty standards. I don't want distortion in my bass sound, at all, though I like tube warmth, which is obviously distortion.
The paraDI does a good job of getting tubby goodness using less than 1/4 of the drive control's travel--a modest amount of blend. Beyond that it was always too much for me, so I backed it off.
I did try it a couple of times with guitar, and found it gave a nice sustain, that moved to fairly gritty.
The only downside I see for this unit as a guitar pedal, is that the parametric (paraDI, get it?) mid control covers a range of frequencies an octave lower than the guitar. You may or may not find this to be a problem. All IMHO.
