Neil: In the environments I've been in I really haven't seen discrimination, and I don't believe it's because I've been blind to any discrimination. That said, it is possible (indeed, probable) that the environments I've experienced are not entirely representative. But, while I've seen women-friendly environments (evidenced at least by the number of women), I haven't seen that lead to many women in programming positions in particular, or IT to a lesser degree. And in the open source community -- where I think there is very little discrimination (because, after all, no one even needs to know you are female), I also see very few women.
One could redefine discrimination to include ways of interacting which may intimidate women... but I think that's expanding the definition of discrimination too far.