I really don't like it. Mostly because all the ones I've seen have been irredeemably awful, but one of my good friends is very fond of it and she writes it well, so it's not all that. Partly I don't like the way slash has to have babies and marriage and all the trappings of a fairytale romance, especially when it's about characters for whom a fairytale ending would be OOC in the extreme (Sirius/Remus, anyone?), and partly it's because it COULD NEVR HAPPEN OMG. I'll have more patience with it if the author concocts an even vaguely plausible scenario - magic gone wrong! alien abduction! - but the classically bad stories where it "just happens" are the ones that send me fleeing for the back button.