It's a hugely unique series IMO. As Weddon has said, the intro with Firefly "rustling up" some cattle "sums up the series in 5 seconds". It's just such a unique blend of sci-fi and western, you'll be suprised that it works, but it does! Another good thing is, I've even known people that hate sci-fi to like it. That might not sound like a plus, but there's enough SF for SF fans to like it, but not so much that people not into SF will be turned off. There isn't a load of technobabble either, Kaylee (the engineer) speaks in, pretty much, laymans terms (more like a greasemonkey than a Trek engineer) and has this cute "hick" accent (well, all the cast except the Tam duo do, but Kaylee is the character that grew on me the most, especially
after "Shindig" - well except for River, hence the DP :P
I wanted to see more by about half-way into the pilot ("what's up with the girl in the box?") and was hooked by the time "Bushwhacked" came about. And I really dislike Buffy and Angel, so if you're turned off by those shows, I wouldn't be turned off of FF.
Check out any of the episode decriptions on wikipedia - there's a lot of foreshadowing and references to previous eps. That might be a bonus to you.
by the time I saw "Objects in Space," I was addicted.
By the time I saw that ep, I'd become very depressed that there was no more Firefly, and that there was more character development in a mere 14 episodes than, dare I say, 7 seasons
of voyager. I was glad to be on the ride though.
I'm almost certain you'll like it, regardless of that SF you're into, I've shown it to people from all walks of life, and all have liked it to some degree, even those whose closest brush with SF was seeing Star Wars ep IV.
Oh, and I'll forewarn you, the theme song will be stuck in your head long after you've finished watching the series (this is a SF series where having lyrics is a good thing, far better than with ENT IMO)!