Yep, this is pretty much what I came to say. I've worked with a lot of fantastic engineers, but also plenty of naff ones who are just kind of there by default.
Most of the women I've worked with in IT, especially older ones, have had to work really hard to prove themselves and made a deliberate effort to become engineers/consultants/etc. As such, I have to say, I can't think of any woman I've worked with who I wouldn't consider very good. But, the same size is sadly very small - lots of women in project management and business generally, but I see very few beyond helpdesk.