Itw as pretty cool how it originally used supernatural occurances as allegories to high school/teenage life. But even better was that it allowed its supernatural nature to make it into a sci-fi show instead of a cheap front and always used the supernatural as a means of conveying very real events in daily life and emotions. Especially coolw as season 6 and 7, where the world of Buffy and all thats he does and knows collides with the 'normal' world. How does a secret super heroin stand in a world that would probably think she's nuts (such as when she needed a loan, got denied, then saved the guy froma demon, and he still denied her the loan).
The show had a lot of depth that people who had never seen it never understood. A friend of mine always wrote it off saying "Yeah, a girl fights vampires. Deep." when a lot of the issues portrayed in the show used the supernatural occurances as catalysts or backdrops to a larger human experience (but again, never used them as a front).
The Body was a fantastic example, whereone was so used to calamity being an actual force, something that could be stopped and had been stopped byt he super heroin, but ended up being somethign completely normal and unstoppable. Even afterwards, the supernatural allowed the concept of fate and death to be explored in ways that a 'real' TV show never could. By being supernatural, it allows Dawn to explore the lessons in accepting death instead of trying to subvert it (by wishing that her mother be brought back to life).
Another one was addiction, as portrayed by Willows growing use, control, abuse, and rehabilitation in all things magical from the beginning of season 2 all the way to season 7.
The show had a lot to offer besides being some campy sci-fi fantasy show (like, say, Charmed...don't hate me, it's just the way I feel). Even the musical episode, which many series have done before, wasn't like the others. Other series make a one-shot musical show with little or no substance fromt he rest of the show, but Once More With Feeling was the musical episode and every storyline converged in that episode. Buffy's true feelings about being resurrected were revealed to her friends (that she had been in heaven before she was revived, not hell as she had told them), Xander's insecurities about his engagement to Anya, Willow's abuse of magic and abuse of Tara's trust, Tara leaving, Giles leaving, and Buffy's semi-acceptance of her relationship/feelings with Spike. Everything important came up in that episode, and no 'joke episode' I dare say, has ever managed to equate what Once More With Feeling did.
There is some fantastic writing and fantastic acting in that show. It's no wonder that there's a film professor at my school who teaches with screenings of Buffy.