Being a bassist, distortion was an effect that I mostly didn't understand-- I listened to a lot of Iron Maiden (bass with no distortion, no pick, and flatwound strings) when I was learning to play, and my father, also a bass player, never liked or used distortion either. My first distortion pedal was actually the same model of ProCo Rat I use (and love) today, without the Keeley mod, of course, and I never knew any better than to turn the distortion all the way up, all the time. I never found much use for it, and sold it after a while.
When I started layering and multi-tracking (and therefore playing more high-end parts), I realized that distortion was a big part of "guitar" sounds, and it took me years to get a real grasp of what to do with it, what the different flavors were, and how they could be applied... moreso than any other type of effect, different distortions have amazing varieties and subtleties. I'm sure, within five minutes of message board searching, you could find heated debates over what constitutes an overdrive, distortion, or fuzz, what a "crunch" pedal is, whether or not a distortion is truly amp-like, etc...
The important thing to remember about effects in general, and distortion in particular, is how important your other equipment is-- live, I play a tenor bass as a lead instrument through a bass amp and cabinet. My needs are very different from both a traditional bassist with distortion and a guitarist; the pedals that make a Fender Telecaster really sing through an open backed Vox tube combo may very well be useless to me.
