I agree that for a Buffy virgin (and while the movie was amusing, it doesn't count) you need to see the entire series. I also hated anything after season five, with the exception of Once More, With Feeling. Once More, With Feeling is so classicly Joss.

And you have to see Angel. Even as much as I passionately hated how they took it, it was still a must see. And if you don't watch it, you don't get to see another classic Joss moment with Angel dancing at a party. Angel is also worth watching for Doyle alone ::drools::