There's a lot of talk in the gamer blogosphere about replicating Firefly in a roleplaying game. I loved the show, I'm looking forward to Serenity, but... I'm really skeptical of the allure of playing it. Now, mind, I've only seen half the series (the other half is sitting there on my shelf, but I must play WoW six hours a day), so maybe the entire dynamic of the television show changes or something, but from what I've seen in Jaynestown and Our Dear Mrs Reynolds, the appeal of Firefly is the characters themselves, not the setting.
The setting is... not bland, but it is generic. Archetypal. It is the lovechild of Westerns and Space Opera. It's... not exactly complex. Further, I can't see any instance of play that would game in the same places that the series went. What is there left to do on Hodgson's World (planet in Jaynestown)? Why go back to... whatever planet had the plague in Train Job? The series' primary characters have already been there, done their thing, and left. If the PCs showed up, all they get is sloppy seconds. Any actual play would require the creation of new planets and new settings. Perhaps you keep the Firefly-designation ship, but... that's not much of a setting in and of itself, is it?
It's the characters that make the show shine. It's Mal and his past, it's Inara and her desires and restrictions, it's the Shepherd and his questionable past. Unless you plan on playing the characters themselves, you're not playing Firefly. Playing the characters themselves I will admit is an option, maybe even a viable one, but I don't think that's what people are after.
Of course, I've never seen the point in playing in the Star Wars universe concurrent to the movies, either (KOTOR has shown me the light of playing in other eras). The story that you want to emulate is about the characters -- if you take out the characters, how can you still say you're emulating that story?