For me, the science in science fiction only needs to feel plausible. When I read science fiction, I'm not looking for stories that are actually accurate based on real scientific knowledge (of the now or the then). I need to believe the world being relayed to me is real, even if the technology within it
is far beyond anything we have today or even impossible based on what little science knowledge I have. Even bad science can be written in a way that sounds good, which I think is more important to science fiction as a social genre than limiting oneself to scientific rigor. SF certainly is about science, but only insofar as it is about how science changes us. For this reason, I think much of the science in SF can be metaphorical rather than strictly factual.
Writing plausible science, however, is never an easy task. More often than not, I think it can be done by being consistent without excessive info-dumping. The longer an author spends talking about how something works, the more likely it is for me to start seeing the holes. That's not to say that info-dumping isn't good to a certain extent. In fact, I'd argue that treating the technology too lightly can reveal different kinds of holes (ones tied to the worldbuilding rather than to the logic). For most writers, I think the balance is easy to manage. I've only read a few books in which the holes in the world's logic were so obvious that I had to stop reading, and most of them were not published by major publishers of SF (or even reputable small presses).
But perhaps my lax standards in regards to science have something to do with the fact that I'm an English major and not a scientist (though I'm no illiterate when it comes to science). I suspect that many scientists are frequently annoyed by what "passes" for science fiction these days. They see the holes all the time, right down to the core.
How about you, though? How important to you is science fact to science fiction?