Firefly was a show that didn't exactly last too terribly long. It did last longer than a few of my other recommendations, but only by a couple of weekends.
The basic premise is that of a group of bounty hunters that have picked up a doctor fugitive and his sister. The movie takes place some time after the series (not sure how long, but Book looked much older) and focuses on the storyline with the doc and sister.
It is hard to say what makes the show so good, but I definitely recommend sticking with it for a couple of episodes, at least. Having just seen the movie last night, I'm incredibly stoked on how good it was and I look forward to being able to see a complete version in September. (They didn't even have the credits ready for the version I saw last night.)