Firefly was actually on the air before Nathan Fillion appeared in Buffy. The reason he appeared in Buffy that year (at the same time Gina Torres was in Angel, and a year before Adam Baldwin was on Angel) was because Firefly had already been cancelled and Joss was giving some of the actors work while he tried to figure out what would happen with Firefly.

So in reality, you have no excuse for not having watched it on the air. :p

I watched every episode as it originally aired on Fox, but they really messed up the order of the episodes, didn't even air the fantastic two-part series opener until the show had already been cancelled, and never showed three other episodes at all. I had to suffer through commercials every ten minutes, and had to endure Fox's episode preview for Our Mrs Reynolds, which indicated it would be an uninhibited, smoldering, trashy, sex-filled episode, which made me want to strangle my tv because it was already clear that they were trying to ruin a great show. It was not an ideal viewing experience. I remember trying to get more people to watch it via wotmania at the time, but not very many were interested.

... fuck, I'm one of those people who watched Firefly "before it was cool", aren't I?