I can say that she's one of the world's experts in the history of Christianity. She will force you to question and challenge accepted belief, which most people think is a good thing. This seems to be the seminar format of REL 251. I know that Pagels runs a seminar very well, which is an argument for this class, but I'd expect there to be more reading for this class, which may not be what you're looking for. But I will say that Pagels chooses her readings very, very well.
Nothing is superfluous or particularly dull.
Consider this course as a more in-depth version of REL 251 if you're already interested in the material. The reading list caught my eye, but maybe I'm just strange. Those authors and more are on the syllabus. Pretty cool, I think. She's passionate, and to boot, she's won an Emmy for a documentary she made.