This article was so-so. They point out that going to bed late allows people to be productive late at night; at hours when they're less likely to get interruptions. This is very true. However, they also fail to acknowledge that early risers can also accomplish things early in the morning before standard work hours, without interruptions.
I did like the point they made that in early societies, having people with a range of circadian rhythms in a community was helpful, since there was always someone awake at any given point, to watch for predators etc. Overall though, I felt the article was more "fluff" than substance. It was interesting but could have made the exact same points while being condensed a lot more.