True, for me author's notes are also more important to decide whether I give something a try if I don't know the author. If I'm already familiar it's only things like pairing and the summary blurb. Though I think for me there is a kind of longterm effect. If that kind of preface happens all the time I find it irritating even if I like the story.And sometimes I notice things that wouldn't have irritated me otherwise, for example a couple of times recently I had author's notes pointing out POV shifts, and normally, I'm not bothered much as long as the narrative is still clear, but the note made me hyper-aware of it then.