Women can definitely be successful here but it is very male dominated. My experience is that to be successful you need to act like all the men around you. This is not only a gender issue but can also be an issue for introverts.
Many of the women at Director or Executive level either have no children or a spouse that does not work outside of the home. Men are congratulated if they work from home or stay home due to a domestic issue.
Experience for women will vary greatly depending on the group they are in. I have had a great experience, did interesting work and am fairly compensated. I do not have executive aspirations, which helped me choose balance. It is a fairly flexible work place in most groups which many take for granted. And 20 weeks mat leave (8 unpaid) with 4 / 8 for men is pretty darn good.
If you want to be taken seriously, do not start in a support role. There is a massive glass ceiling above all support roles and near impossible to break out of them, regardless of skills or experience.
Ability "choose" work hours or flexibility is completely dependent on your current manager. Good manager = good work/mom balance. Not awesome manager = crappy work/mom balance.
I have worked here for 5 years and there are quite a few women here but mainly in lower level roles. Generally I believe they are treated fairly but management is male dominated an not diverse. Some managers treat women differently than there mail counterpartes