I work for a non-IT company with a small IT department. We have one woman on our team.
Here are some things that I have noticed.
Completing a Task:
When one of the guys gets a task, we jump into it immediately and release something quickly (even if it doesn't work).
When the woman on our team gets a task, she thinks about it, asks for some help, comes up with a solution, and eventually releases it in perfect working order.
One would think that the woman is doing things the right way, a working solution that takes 2-3 times longer to produce will always beat out a nonworking one.
Unfortunately, others may see her as being slow and inefficient. In addition, one of the cardinal sins in IT is asking for help, once you do that you are seen as weak and unintelligent.
Team Socialization:
On a slow day, all of the IT guys will somehow converge into someones office and talk about random stuff, sometimes work related, sometimes not.
Rarely does the woman on our team join in unless we somehow managed to converge within her office, in which case she usually stays quiet unless asked for input.
I am not exactly sure why this occurs, but it is hurting her career as socialization within the team is one of the easiest ways to gain recognition and respect.
Performance Review Time:
Come performance review time all of the guys are on high alert.
We do PR engineering, damage control, boasting, extra work, and anything else needed to get a good appraisal from upper management.
The woman on our team simply continues on with her normal routine, sometimes asking one of us in private whether it's that time of the year.
Who do you think gets a better raise?
Personally, I think if you want to succeed in IT you have to be aggressive (taking control of each situation) and relatively thick skinned (ignoring egomaniacal VPs without losing sleep).
You have to be able to socialize with people within your team and outside, while at the same time not losing self dependency.
I am not sure if women want to work in that kind of environment.