diaglo said:
i can't say enough bad things about it.
I concur, but hope to be a bit more diplomatic about it.

For the record, I've read through the corrected 4th printing and have played four sessions of the game. All this is IMO.
Basically, there's a RPG and a license crammed into the same book, and neither really have anything to do with each other. Any
Firefly-like story you get out of playing the game isn't going to happen because of the rules. If anything, it will happen in spite of them.
On top of this, the rules felt really shaky to me. The task resolution is very basic pass/fail and very random, even with use of Plot Points (the game's "fudging" resource for players). It was also really easy for our group to twink PCs for combat effectiveness. Advantages (whatever the term is in this game) of the same cost are all over the place in effectiveness. Ditto equipment; e.g., there is no reason not to wear ballistic mesh that we could see.
The GM advice also really honked me off. It felt very '90s to me. Based on it and some comments from Jamie Chambers here on ENW, it seems to me that, like a lot of '90s-era "lite" RPGs, this is a game that intends for you to largely ignore the rules and let the GM push you through a predetermined plot. Which begs the question of why you'd shell out the $40 for the book.
My advice: skip it, and pursue alternatives. I sold my copy.
If you want to go the traditional route, there's nothing that
Serenity does that your d20 RPG of choice won't do better. GURPS would probably do fine, too. Even HERO if you dial things right.
If you want to branch out a bit, I think
Spirit of the Century is a great fit for Firefly.
If you want to go crazy-hippie, I'd suggest
Primetime Adventures. I've heard people have had success with hacked
Shadow of Yesterday and
HeroQuest, too.