I had forgotten about her using magic in S3, although I remember Xander using magic in BBB in S2. which reminds me that the way things went re: Dark Willow seem foreshadowed and inevitable from the beginning (once you've seen the whole series) but really weren't; Joss had been undecided if he wanted Xander or Willow to "turn gay", and Xander could have easily have been the one to turn "dark" - I'd say he has a much darker (and sometimes nastier) streak to his personality than Willow; but he's also far less repressed about it than she is.

Of course I haven't rewatched any of S3 since the first watch, except for Dirty Girls, bits of Graduation Day, Earshot and The Wish. (Which I absolutely adore.)