A New York Times article reports on a meta-analysis (a formal statistical analysis of many published studies) that concluded that organic foods were no safer or 'better' for you than non-organic options. I think the article (and the study which I have not directly read) raise important issues.
In Eating Our Way to Civility, one of the guidelines is 'eat organic if you can'. Eating lower on the food chain is essential and grass fed beef is going to be better for you and the animals. However, there are many things, other than nutrients that organic food support. For instance, the ecological benefits of using fewer pesticides must be factored in, and the social benefits of organic growing and community agriculture were not considered in the study. Including such 'externalities' should be discussed as well and I rest by my suggestion of "eat organic if you can".