So last night I ran a Serenity campaign, using the rulebook that was my Christmas present from Tanya. (She got it signed by Joss Whedon!! We are such nerds.)
Anyway, it went pretty well, all things considered. My players are enthusiastic enough that the GM is almost like an appendix. They will play even without me. That said, they chewed through my plot at an alarming rate. Not unlike the movie, every time they'd get almost done with a task, something would happen and they'd have to scramble. Which was fun, and kept everything rolling along at a pretty healthy pace, but made me wish I'd been a bit better prepared.
The system itself has some quirks. Skill/Attribute rolls are based on die size. As you get better, you use bigger dice, so your chance of success goes up for simple acts, and more complex acts become available. Thus: a d4 is a pretty crappy grasp of a skill. (You can only do simple stuff, and maybe not even that). A d8 is a pretty good grasp - you're a talented amateur. A d10 is a professional and a d12 is a prodigy.
Traits and Complications add or detract from your base skills. What is odd about the system is that this is not done through addition/subtraction of hard numbers, but through stepping up or down the die size. Bit of a brain bender to those of us used to AD&D and GURPS.
The best part by far, though, is the addition of Plot Points to the game. These work kind of like experience points. (We tracked them using pennies.) You can eventually spend plot points on enhancing your character. For the purpose of this one-off, however, the real joy of plot points is spending them to beef up a particular roll that you really can't fail on.
"What do you mean the privateers are right behind us? Tina, get that gorram hydraulic boot back in place right now!!"
"Roll for it and pray."
"Fuck prayer. I'm using a plot point."
Anyway, I give it one and a half thumbs up. I haven't read all 200 pages of the rulebook, and it was certainly playable without that (for an experienced group). Having only 2 copies of the book hampered us more than usual, since no one knew the system. Because of the influence of plot points, anyone who might have like to fight about the rules just spent a point for the safety margin it affords.
My only complaint was that the layout of the book made it a little hard to GM. The book reads in a rambling, conversational way - which makes it easy to read but hard to skim. The index is less helpful than I'd like. I resorted to flagging relevant pages with post-its.