The rules are decent, but the later revisions and additions that came in the Battlestar Galactica RPG are WELL WORTH YOUR WHILE!! They revise how the Perks and Flaws work (or whatever they are called in this game, can't recall off the top of my head); they now follow a similar dice-step system as the skills & attributes. There's also a huge bonus in the Starship combat rules, something severely lacking in Serenity.
My group played Serenity when it first came out, and it was a blast though. The system is dirt-simple, and as long as you're not totally stingy on Plot Points, the gameplay is fun too. The only issues we faced (and they were easily fixed) were:
- Don't call for a dice roll for every little thing. Only when it's dramatically appropriate. It's pretty easy to fail a roll, so making a super-skilled pilot roll to do a simple docking procedure when there's no stress is pointless.
- Don't be too stingy on Plot Points. They are fun to have and spend. Don't be too nice about it either. I HIGHLY recommend checking out the additions to Plot Point rules in Battlestar Galactica RPG.
- The economics of a ship are kind of weird and spread out all over the place in the book. I compiled it all and revised it to make a little more sense: as is, owning a ship and running a successful business with it is nigh impossible unless the ship is ALWAYS fully loaded. I mean, obviously it should be hard to break even all the time, but it shouldn't be impossible, and the way the game stats out prices, it's damn near impossible to even theoretically break even, which is kind of messed up (who would run a shipping business if it's chance of failure is like 90%?).
Sorry if I concentrated on the bad points, because it's definitely a great system. Stays nice and quiet in the background while the Plot Points drive the drama and player-control of the story, which is something you don't always find in mainstream RPGs.
I haven't read the Serenity Adventures book, but Out In the Black was pretty decent. Poorly named (it's 99% planet-bound adventure), but aside from a few logical gaffes, it's a very fun Western-themed story.