Can't know they're crummy 'til you've heard 'em, and usually there's something which leads to giving 'em a listen to begin with.
Yeah, I've bought things that I've considered mediocre, poor, or crummy. You have to take chances or you'll miss out on a lot. But once I peg something as not so hot, I definitely don't keep listening to it. That's what I meant.
Also, I listen to music as music. I try not to confine myself to a few genres and accept everything within those genres. Hope that doesn't sound pompous or self righteous.