Having a four day week is called working for the government around here
In all seriousness, I don't think a national four day weekend is ideal (someone mentioned avoiding traffic, which can't happen if everyone still left out at the same time). However, everyone is different. If you're the kind of person who burns out as far as productivity goes, an eight hour day is better. If you're someone who can work long hours, a three-day weekend is better. I'm partial to "as long as I get it done." If I work longer hours or more productive hours, I should be able to duck out early. But every job is different and every person is different.