I always had mixed feelings about the TV show "Firefly". On the one hand, it had great chemistry among its characters (something that "Enterprise" sadly lacked). On the other, I've never been a fan of "horses and spaceships" space opera. In any event, the point was moot, as the show was inexplicably cancelled before any reasonable person would expect a large audience to grow.
So, I was very curious to see the new Serenity movie, and I must say that it's one of the best SF movies in recent years. (Notice that SF doesn't include Lord of the Rings.) In many respects, I'd put it up with the best of Star Wars: it has a great feeling of concrete reality to it, the characters' interrelationships are interesting and the viewer cares about them, there are actually reasons behind the things that happen (someone thought about more back story than appears in the movie, though I wish someone had spent about five minutes thinking through the movie's "geography".), and there is a point to the whole exercise. In some ways, it's better than Star Wars: more mature, three-dimensional characters, a palpable feeling of risk (that characters aren't necessarily safe just because they're main characters), and a ending that is satisfying beyond the old standby, "those bad guys blowed up real good".
I think I'll buy the DVD version, which is something I don't do very often (excepting the kids' movies).