Currently finishing my doctorate in clinical psychology and having received my BA from UCSB, I have been very interested in using EP in the clinical psychology context. Currently, Theodore Millon has a strong theory that is grounded (though loosily) in EP (if others are familiar with Millon's model, I would be interested in hearing any opinions others may have in regards to EP). I use it as a core foundation for my work with clients, especially in regards to case-conceptualization. However, presenting the approach to patients is very trick and I usually am very resistent to providing them with it. Although especially problematic for those with strong religious leanings, most patients equate evolutionary thinking with athiesm and it can be detrimental to place one's own views on a patient.
Aside from the few patients I see in a anxiety and stress disorders program, the core of my patients have been sex offenders and EP can be used for conceptualizing these patients, but it would be VERY dangerous to provide them with an explanation of their behaviors in EP terms ... doing so would be similar to providing a psychodynamic explanation ... it does little more than provide a rationalization and justification for their behaviors.