I have a passing acquaintance with Cortex Plus — I read the old Serenity book and so learned the Cortex system once upon a time, and I've thumbed through the now-defunct Marvel Heroic Roleplaying, but I've never actually read nor played the system before interacting with the new Firefly RPG.
The system is fast — it's narrative-driven, meaning that a given action tends to last only about as long as you need to thoroughly describe it, and if necessary, roll dice to resolve it. Coming more from a traditional gaming mindset, and only playing for a one shot, we didn't mess with all of its action economy — taking penalties or conditions to get Plot Points, building Assets, and so forth. But we started to get the hang of it by the time the game ended, meaning that we'd probably be some free-wheeling mess of complications and temporary bonuses in another game or two.
Being a little more story-game than most, failing and taking penalties means that the story continues even if things have just gone south — one bad roll won't bring the game to a grinding halt, although it might take it in an unexpected direction.
Overall, it seems like a system that does what it sets out to do. If you like a lot of granularity in your rulesets, or want to micromanage resources in your best Oregon Trail impression, this game doesn't look like it will do it (at least, not without some fiddling). Also, given the limited exposure, I also don't know if it has anything for teamwork — I was playing a former politician, a social-heavy character, but I had too much overlap with the former companion to do anything too noteworthy. I don't know if there is some way we could have synergized our actions to overcome that issue. However, if you want to tell a free-wheeling action story or a gripping drama, you could do it; the rules are fast and don't get in the way if you just want to role-play. Plus, I'm always in favor of fast combat resolution.