I did many years of 4 day work weeks, although I was hourly (and doing a "less skilled" labour type job). It was pretty much a 24/7 type operation, so everyone would have four days of work in a row, but would be evenly distributed throughout the week. Everyone loved it. It was 10 hour days (40 hours a week) vs a normal shift which would be 8 hours (but 5 days a week). That extra day off a week is totally worth the extra 2 hours a day.