How about these categories
I enjoy this thread, the discussions even when a bit heated all do bring something to the playing field. I can't remember if this was proposed in the past, but how about 4 categories of SF like the following:
Science Fiction - rigorious hard SF of the type Baxter writes (or Clarke) where everything is either well known, or a not-so-great leap from that.
Science fiction - Good science which is important to the story, perhaps to the point there would be no story without it. Maybe the Moon is a Harsh Mistress would fit here, though probably better above.
science Fiction - Where science is there, possibly even central, but can be left as either assumed or handwaved away and that the emphasis is on the people and the lives they lead. Hyperion perhaps
science fiction - This would be about the place were a story begins to blur between SF and fantasy. The science is there and can serve as a backdrop but is also subsumed to support the story even if it made a scientist cringe.