I recently started working a 4-day work week and gained some great feedback here: https://news.ycombinator.com/item?id=9505868

Rather than use the 5th day as a casual, side project workday as it seems the author of this post has done, I decided to take the day totally off. So far it has worked fairly well, though I have had to check in a few times (as I am currently doing).

The most important factors of my decision to experiment with the new schedule was that I have a 4-month old and want to spend time with her and my wife. I was also pretty confident that I didn't actually have enough work to fill 40 hours and was spending a good amount of time reading news or whatever else from the office when I could be hanging out with my family or enjoying the outdoors.