Newsweek's Sharon Begley has this very nice article* about why one should be wary of results evolutionary psychology. The reasons Begley gives for this are 1) the assumptions made by many evolutionary psych results are shaky, but people don't often question them because they believe/want to believe them and 2) the claims made by evolutionary psychologists are often untestable and have been proven false by examining people living primitively today. (She gives great examples, debunking the myth about men liking women with 0.7 waist/hip ratios and others; see the article.)
As someone who had recently gotten into what Begley calls "Pleistocene just-so stories" that people like to believe because they are interesting and sexy, I learned to be more wary of the premises of such "results." As evolutionary psychologists are model builders, it is important to recognize that these are models whose assumptions should be rigorously questioned.
* It is surprisingly insightful and nice for something as mainstream as Newsweek. It was so good I considered writing to her; I also considered jumping up and down.
** I found Miller's The Mating Mind a fun read.