If you enjoyed the original Star Wars trilogy with it's camaraderie or the likes of Cowboy Bebop with a hint of Blade Runner, Aliens and the constraints of Red Dwarf then you're pretty much guaranteed to enjoy Serenity.

I've never seen Firefly but that doesn't stop this from being one of the best popcorn movies I've seen for a long time, the characters are easily identifiable and the storyline is easy enough to get into and follow.

Unlike wpqx though with his civil war analogy, I saw it more as the USA as the alliance with the rest of the world as the Independents (probably because I'm not American) and because as River commented when told that the Alliance were trying to improve everyones lives, "We're meddling, making the assumption that everyone should be like the alliance". 

There is a huge Western influence running throughout the film along with a fair dose of humour, the Space battles are on a par with anything from the Star Wars series. Overall despite its obvious TV heritage it's a great slice of entertainment.

Cheers Trev.