Ooh, good start. I wasn't that big a Buffy or Angel fan, but I saw enough to know that Xander isn't just a construction worker out of a job. And (if I recall correctly) Giles is the professor who guided Buffy and her friends in their battles against the forces of darkness. There's a lot of dramatic potential here, and I'm also eager to see where you go with it.
One of the interesting aspects of Superman's invulnerability in the comic books was his susceptibility to magic. Might this weakness show up here also? And how deeply will Lois be involved? Will we get to meet Buffy or Angel?
Like I said, lots of potential. Keep it coming.
Very interesting start.