First, because Vaillant was ultimately unable to answer his research question, Shenk's article reveals the complexity of psychological research and cautions future psychologists against looking for simplistic answers. Second, it highlights some parts of psychology that are considered woefully out-of-date, which serves as a caution that even the most cutting-edge theories may be found to lack support. Third, it describes a successful longitudinal study, in contrast to most psychological studies that focus on college-age students. The fourth reason the study should be included is simply because it is interesting; the study followed the lives of some men that went on...

The final reason the study should be included in the curriculum is that it serves as a great reminder that bias informs every part of how a researcher approaches a study, and a good researcher remembers that he can never eliminate all bias from a study. Because Shenk's article provides such helpful information about the field of psychology, it should be included in the curriculum.
References

Shenk, J. (2009). What makes us happy? The Atlantic Online. Retrieved from http://www.theatlantic.com/doc/print/200906/happiness