In the series you get to know the characters in a way that just isnt possible within the time constraints of a film. I think the episodes are done in such a way that the ending isn't as important as how they all got there (in fact a few episodes start with the ending, then go back and explain it). So if you liked the film, you should love the episodes, and I doubt foreknowledge of the future will spoil the witty interactions which make Firefly great
