I would welcome more women in CS, as long as these are not "quota women" (that are given easier examinations as happens in some places these days). When I did my PhD, we always has some competent women there (about 1:5) and while it does not add on the scientific side (they are just as smart as the men and do not think in any relevant way differently), it does add on the social side. For example, this mix resulted in two, now married, couples and it decidedly produces a nicer atmosphere on any social activity, and may that be just a coffee-break. And on the pure scientific side, while I have yet do discover any different "female" scientific mind-set or way of thinking, even if it is just 20% more scientists, it is 20% more ideas, interesting people, etc. and it would be really stupid to lose them.
But in the other side, I just do not see any evidence (and the women in CS I know did neither) that women are actively prevented from entering the field. I did however hear from several of these women engineers and scientists that "the ladies do not want to work hard" was their personal explanation for the disparity in numbers, usually with expressions of significant disdain and concrete cases to give as example.