Carina and I became fans of Firefly, the show from which this move grew, when we borrowed the DVD from our friend Eric. Written by Joss Whedon (of Buffy the Vampire Slayer fame), the series was a phenomenal blend of witty dialogue, complex (and often unpredictable) characters, and interesting plot developments. It was unlike most traditional television, and the exceptional writing did a lot to ensure that.
The movie holds true to the series. The first scene aboard Serenity, the titular spacecraft, has impeccable pacing, and the entire theater was laughing out loud for several minutes. The actual opening sequence is a real storytelling gem, with layer upon layer of visual and thematic content. In just a few minutes, a great deal of exposition is accomplished, and done so in a very organic way, so as not to feel rushed.
Serenity, as a film, stands on its own. Viewers need no prior experience with Firefly to enjoy the show. All of the requisite backstory is presented. Those familiar with the series, of course, will get the most. The richly developed characters are true to themselves throughout, so you're sure to see your favorite quirk from your favorite character. The story expands on the River Tam plot, so fans of that story arc have a lot to look forward to.
Oh yes, and Reavers. There are reavers, the unambiguous bad guys of the series, in this movie. One of my few complaints against Firefly was that everyone was clearly afraid of the Reavers, but very little was given to us, the audience, to make us afraid of them. You never see them, and the only real encounter that the crew has with them is mostly just a chase scene. The movie changes that.
I'm looking forward to seeing the film again. It's definitely worth a paid ticket to see, and I certainly want to show my support of the film.