As a huge Buffy fan, I am willing to give this a chance. I will admit that the original movie was not that amazing, and could be improved upon. And, while I like Joss's work a lot, he is not the only worthwhile talent, and has had his own share of duds (see: Titan AE, Dollhouse).
One of my biggest worries is how they will handle the generational aspect. Buffy was always extemely contemporary, which worked well in the 90s. I'm not sure how that aspect of her character will translate to the FaceBook generation.