I'm in the early stages of trying to make it work. I'm at a US IB, in a senior role, and they're being amazing. I do get the feeeling I'm a bit of an experiment for them but this is a good thing.
I took the job after 5 years of not working/working part time, and was totally up front with them at every stage about what I was willing to do. I didn't apologise for wanting flexibility (I do 5 days, but one from home - working towards 2 from home, and leave early most days - i.e. around 4), and made it clear that if they wanted me they had to be flexible. After I got the job I had a coffee with a super senior man from the States, and even he said that I could leave early then log on from home in the evening if it suited me better. I nearly fell off my chair.
I think this long hours approach is from the dark ages. In these days of blackberries and related technology, there's no need for people to sit in an office endlessly. Also, after having 3 DSs I am super efficient, don't muck around when I'm working at all, and can easily do in 35 hours what I used to do in 50 hours.
Goes without saying that I have a great nanny and I don't do ANY housework (yippee!). I'm around alot for my kids, and totally focused on them. Am also fulfilled by a stimulating job AND feel like I may, in my small way, be making a difference to women coming up behind me. Have already allowed one of my staff to WFH one day a week and this person doesn't have kids; I think flexibility should be for all and not just mothers - it's so good for people's motivation.
Mind you, I haven't come across ANY other women with kids in my environment which is a bit odd. Oh well. I like to feel like a pioneer! I also have a strong sense of my priorities - if the job doesn't work or becomes less flexible then I'm off. It's been a few months so far.
So all in all, I think things are improving. But it's up to us to push the envelope ourselves if we're in a position to. Ask for as much as you dare - they can only say no! I don't think women should have to apologise for wanting flexibility. If a good business case is made out, an employer should be willing to give it a go, with the exception of law firms who are just hideous! I nearly didn't go to the interview for this job as I didn't think that it'd offer me the sort of control over my work pattern I need - just goes to show.