When I pick a book to read it's usually dark and erotic. Plot is good. Sex is good. Plot and sex is great! However, when I pick a fanfic to read, I generally go with the one-shot. I rarely invest my time in a story that has more than a dozen chapters, and even then, the writer has to be exceptional. I have to agree with Knorg, that when I'm here, I'm just looking for something that'll get me wet. Of course, I'm not going to waste my time on a train wreck, but plot and character development are simply icing on the cake.
When I write, I write erotica. To quote my favorite blog, to be erotic fiction - sex has to drive the plot. If you can take the sex out and still have a viable story, you did something wrong. That doesn't mean that I write PWP. Even my one-shot's have a reason for the sex, if they didn't they would be porn - not erotica.
While I can understand that everyone has different tastes on the matter, and I generally live by the maxim 'to each their own', I find myself a little annoyed when people assume that just because a story is labeled a PWP or one-shot or what have you, that it's not worth their time.