The movie rocks! Even my wife (ardent SF hater) loved it - although there were bits she needed to leave the theatre for, but that's owing to being 8 months pregnant and having a baby doing loop-de-loops in time to the fight scenes is uncomfortable.
I haven't seen the TV series, but will definitely getting my hands on those DVDs.
The best ...
* The quips.
* The fight scenes.
* The chase scenes.
* The badguys.
* The (kinda) good guys.
* The way the girls have nice outfits as well as daggy work wear (my wife made me say that one).
* The mix of old and new, shiny and dirty, riches and squalor.
The worst ...
* Some of the stuff that would be obvious from the TV series (e.g. Reavers) is really unexplained, even for a SF movie. But it is tied up nicely towards the end.
* The explanation that this is all in one solar system - that makes some things easier to stomach (ALL of the reavers following Serenity), and others harder (the Alliance not nuking the reavers' spaceyard).
* The occasional mandarin word - it was a little hard to follow what was said due to accents and mumbled voices, throwing in incomprehensible Mandarin just made that harder. I had to repeat a bunch of Mal's lines for my wife as my yankee-speak ear is better than hers.
Overall, very watchable and well worth seeing again to see bits I might have missed this time. The choice of badguy was very cool, the overall mix of high-tech and frontier worlds was refreshing too. The way the characters were all mixed up real people was sheer brilliance!!!
So, who else is going to start a Firefly/Serenity game with their local players?