Everyone here is arguing about whether or not there's gender discrimination in the workplace, but... in this context that isn't actually my main concern. Even if there is tangible and quantifiable discrimination in the workplace, something I don't have much interest in arguing either way, I don't support a quota system, because I quite simply don't think the ends justify the means here.
Quotas mean, by their very definition, that gender MUST be considered on an application over other factors, legally. One can sort by merit, and find that they've messed up the required balance and have to specifically change their hiring to be suitable for the quota, but the opposite isn't the case; focusing on what actually makes a person suitable for a job is potentially restricted, hiring someone instead based on their gender is not, and may in fact be required. This isn't acceptable to me. Countering discrimination with further discrimination does NOT make a non-discriminatory atmosphere, just one where two discriminations are battling it out, and I'm one of those equality-of-opportunity-under-the-government guys: I think that if we ever want a really equal society, the lawbook shouldn't be arbitrating on matters of race and gender. It's wrong when laws specifically hold women down -- it doesn't become any more right because the target is shifted.