Started poking through the (relatively) new Serenity RPG last night... Still not sure what my feelings are about it. It's clearly geared towards drawing fans of Firefly into RPGs, rather than the other way around. Consequently, the stats are relatively basic; PCs, which are supposedly the biggest and baddest of characters in the game, typically have only a half dozen skills or so and two or three edges and flaws a piece (here called Assets and Complications).
Intentionally or not, Serenity seemed to remind me of another Joss Whedon/RPG crossover, the Buffy the Vampire Slayer RPG. Similarly streamlined stats, rules for varying levels of power in the game (typically on a 'crew wide') basis. Licensed RPGs, like licensed video games, have never had a lot of appeal for me. With a few exceptions (such as West Ends great d6 Star Wars line), they tend to feel a little sketchy. The licensee typically can't go to far beyond the background provided by the brand, and it often feels like the intent is to cash in a few bucks on a current trend.
On the other hand, there are some things about Serenity that I definitely like...For one thing, I like the idea of the ships in the game being characters themselves, with many of the same traits (like Assets and Complications) that regular characters have. It provides a neat way to customize ships, and makes them feel a bit like the creaky, temperamental hulks we know and love (like Serenity and the Millennium Falcon in a way that most vehicle customization schemes never really achieve.
The second neat idea in Serenity is the Plot Point system. Plot Points work like the ubiquitous luck/fortune/character/karma points that a lot of systems have, but with a twist. In addition to providing a mechanical bonus, like a bonus to a die roll or a reroll, Plot Points can be used to let players tweak the game by introducing minor wrinkles in the plot. For the price of a single Plot Point, the owner of a bar might turn out to be an old acquaintance when a character is broke. For a few Plot Points, you might manage to pull some additional, desperately needed resources out of your back pocket. For a big heap of the things, improbably circumstances will align to save your sorry ass from certain death. It's a neat idea; similar to Fate Points from WFRP, but with wider application. I've never been too thrilled with how Fortune Points work in v2, so I might just 'borrow' the idea at some point.