I recently read the IEEE paper "How to be a Star Engineer" (Google it, it's a great read). The researcher conducted a study on common traits shared among the industry's top performers. Turns out that being extremely intelligent was not really a significant factor. In fact, the star engineers failed to demonstrate a commonality in any of the traditionally emphasized areas of cognitive, psychological, social, or organizational superiority. It essentially boils down to how they used their existing skills in a smart, positive manner. Effective teamwork and communication are listed as huge factors, so I don't see how an IQ test can really be the magic bullet to finding a great employee.