This article isn't very convincing. (I'm not saying he's wrong.) His point is that working less makes you happier and more productive, but he doesn't really talk about how or why or give any cases illustrating such. All he really ends up arguing is that overworking is bad, which is nothing new.

For what it's worth, though, I agree with what he's trying to imply. If the amount of time you work is increasing by n and your work quality is decreasing by n^2, you're screwed.