Wow. I have watched Serenity twice so far, and it is better than what I expected, and I had pretty high expectations. Joss Whedon has proven once again that he is the current master of story and dialog. For the last 1/3 of the movie, I actually believed that it was possible all the main characters would die by the end of the move. It’s exactly what it should have been, Firefly, but bigger, darker, and with better special effects. I will go so far as to say Serenity is the new Star Wars, except what Lucas managed to do by accident, Joss has done with skill and vision.
If you like sci-fi and haven’t seen it yet, go out and buy the DVDs, watch them all as fast as you can, and then go see the movie.