Exaggerated claims: "One particular gene, referred to as the COMT gene, could to a large degree explain why one child is more prone to be a worrier, while another may be unflappable" [emphasis added]. In reality, what kind of COMT gene you have, if it is relevant, is an extremely minor influence by itself on how much you worry. The particular variant of the COMT gene being discussed here is very common, and like all other common genetic variants, it has never been shown to have a large, or even medium-sized, influence on any behavioral traits.
Cherrypicking the study with the most dramatic results: "Other research has found that those with the slow-acting enzymes have higher IQs, on average. One study of Beijing schoolchildren calculated the advantage to be 10 IQ points." In 2013 it should be regarded as journalistic malpractice to write things like this when the average of all the studies on this gene and IQ show the effect to be, at best, a tiny fraction of 10 IQ points. In an analysis that included almost 10,000 subjects from two countries, in fact, a team of colleagues and myself found virtually no evidence of any effect of COMT on IQ.
Idealizing your favorite study: "In other words, the exam was a perfect, real world experiment for studying the effects of genetics on high-stakes competition." In reality, there are no "perfect" experiments, and the one Bronson and Merryman report on had only 779 subjects, which might seem like a lot, but is almost certainly too small to learn anything reliable about genetic effects. About 100 times more participants are needed to really answer these questions.
Labeling genes with behaviors and pretending that possessing a genetic variant makes you a particular type of lucky or unlucky person: The two variants of the COMT gene are labelled "warrior" and "worrier" (for the different responses to stress they supposedly cause people to have—get it??), and then people are in turn labelled as Warriors or Worriers based on their genotypes. That's tantamount to calling the variants of APOE the "Doofus" and "Genius" genes because one makes you more likely to develop Alzheimer's disease while the other offers some protection against dementia. No, wait, it's not, because APOE has a highly significant effect on Alzheimer risk that has been replicated over and over by independent researchers, but COMT's links to the behaviors discussed in this article are smaller and more tenuous. Later we are told that the Worriers' "genetically blessed working memory and attention advantage kicked in. And their experience meant they didn't melt under the pressure of their genetic curse." I thought we gave up on this kind of superficial genes-as-personality-types-and-blessings-or-curses kind of science writing years ago.
Contradicting your own point: "... we are all Warriors or Worriers ... In truth, because we all get one COMT gene from our father and one from our mother, about half of all people inherit one of each gene variation, so they have a mix of the enzymes and are somewhere in between the Warriors and the Worriers." (Is anyone else reminded of the camp 1970s film "The Warriors," about gangs that roam the New York City subways?) We can't all be one type or the other if half of us are both. And incidentally, the pattern of 25%-50%-25% of the three genotypes does not arise only because we get one allele from each parent. It also depends on the frequency of the two variants being about 50% each in the population, which it happens to be in the case of this COMT polymorphism.
Pretending that what has been known for generations is a new discovery: "Stress turns out to be far more complicated than we've assumed ... short-term stress can actually help people perform ..." And later: "It may be difficult to believe ... that stress can benefit your performance." But psychology textbooks have long taught that the level of arousal for optimal performance is moderate, with too much arousal or too little leading to lower performance. This is called the Yerkes-Dodson Law, and it was originally proposed in 1908. Perhaps worth a mention?
The article makes much of findings that "those with Worrier-genes can still handle incredible stress." This would only be surprising if COMT had such a strong effect that it could determine what kind of person you are. But COMT doesn't have that effect. It's surprising when someone with the genotype for brown eyes has blue eyes instead, because the relevant genes almost completely determine the phenotype. It's not surprising that people with one of hundreds or thousands of genes that make one susceptible to stress turn out to be able to handle themselves just fine.