What do you think of 4 day work weeks?

I like the idea of them for sure but think it depends on how they're managed. Some companies keep pay the same but reduce total hours, so four eight-hour shifts, effectively creating a raise at an hourly rate. Some just do four ten-hour shifts. I see arguments for both sides but think the work-life balance could be a lot better for a four-day work week. If I was at a company that had the option of trying it out, I would. However having it as an option could create some difficulties, i.e., "We can't hold this meeting on Friday because Janic is on the four-day schedule and isn't here."