I've been fortunate to have the flexibility of moving to a 4.5 days a week at my work to help with childcare. I have Monday mornings off and then work the extra time across the rest of the week.
Some weeks it can be quite tiresome by the time it gets to Thursday/Friday, but having been able to experience it so to speak, I wouldn't change it. Better on the wallet and more time with my son even if it is just for a few extra hours.
I don't think my place of work will change to a 4-day week as standard. There's been talk of it and research into it, but I don't think it'll be feasible. At least not for the majority of departments anyway.