All I know is what I say to people when this comes up sometimes. I don't do yaoi. It's questionable whether I do slash. What I do do, is characters who happen to not be straight. Yaoi terrifies me slightly because it seems from where I'm standing that it's not about the characters, it's about the sex, it's about who's seme and uke, it's about... and here is private in-joke time... how pretty their nipples are. And that's maybe where all the OOC fic comes from because it doesn't matter how they get to the sex, just that they do. For me, it's the interpersonal relationships, how they play off each other, that's interesting.
I mean, sex is good too, obviously. But they shouldn't just see each other and become overcome with lust for each other's sizzling man loins. There should be extrapolation.