It is interesting, but then you get into jobs where you cannot shorten the work week, such as Police or TSA workers or other such things. There are tons of thankless jobs that pretty much are built around having to work the 40(+) hours, some just require travel, some are hard to get people to apply for (honestly, when was the last time you thanked the TSA people at the airport for making you take your shoes off and scan you, or the cable guy who had to rerun the wire from the pole to your house in the dark at 8:30pm).

I would love to work only 5 hours a day, although i might get bored. I guess it might work better with salaried employees.