I can tell you I've seen some highly-qualified females. This one is probably smarter in computers and mathematics than most of us combined:
Xiaoyun Wang is the scientist continually finding collisions in hash routines.
And then there's this chick who published her first math paper as an undergrad. Never mind, I shouldn't post the picture I want to here. Just google up actress Danica McKellar. Straight to this subject, she's written books to try to get girls motivated in math, and even tutors them over the Internet.
I’m sure that out of a thousand or so male computer geeks there exists a female one, but I have never met her. That’s why I qualified my statement with “personal experience.” It’s also why I don’t worry, since the theoretical skilled computer geekette would have no trouble landing a job based on her skill. I for one would hire her just for the rarity factor.