From Steven Aftergood at FAS and passed along for you a CRS.
http://www.fas.org/sgp/crs/natsec/RL34333.pdf

This report is intended to provide information that might be of interest to Congress on the current debate surrounding the creation of special U.S. Army units and organizations, which some believe are needed to address current and future security requirements. While the Army has recently changed from a division-based force to a brigade-centric force, it has resisted the creation of special units to deal with counterinsurgency, stabilization, and training/advisory operations. In contrast, there have been a number of proposals to create new units and organizations better suited to address the challenges of these mission areas. Secretary of Defense Robert Gates’s recent challenge to the Army to organize and prepare for asymmetric warfare and advising and training foreign armies could renew and elevate this debate.