I work for Treehouse. The 4-day work week is amazing and I feel it'd be very hard to go back to 5 days a week.

What do I do on my Fridays?

If I have errands, they get run. I usually pop-in and off my computer. Sometimes I actually am working, but I'm "playing". I'm a data scientist and I love my job. I love working on my tools and I love trying new methods. So I might be improving my D3.js skills. Or learning Python (like I have been). Or teaching myself new Bayesian analysis, or survival analysis methods. So in once sense I work on Fridays, in the other hand it feels like play. And I'm not obligated, so I can get up whenever.

Also, this isn't every Friday or weekend. Many weekends are just non-tech play, like a trip to Boston.

In general, my stress level is way down. I feel focused and happy to be at work when I'm "there" (I work remotely, another Treehouse core value). I think about Treehouse, much more than 4 8-hour days a week, but it's so much more pleasurable! I'm totally thankful to work for Treehouse.

I've worked 40 hour weeks in a corporate environment (where it's often actually less than 40), 60 hour weeks in an agency, 32 hour weeks at Treehouse. I find that needing to physically commit to work five days a week is the crux—it makes very little difference how much time you're spending in the pursuit of it. I'm big into backpacking, so three full, available days makes a world of difference to me, not the amount of hours I'm expected to work.

I would think it depends on what you want to do. If you want to go for longer hikes as someone else commented it would be great. If you want to pick up your kids from school every day, maybe the reduced hours version is better.