A novel physics curriculum, Matter and Interactions (M&I), was introduced into Georgia Tech engineering physics courses in Summer 2006; today the curriculum is taught to approximately one thousand students each semester.  We will highlight some key issues associated with implementing the M&I curriculum. We will also describe efforts to measure the new curriculum's impact using both standardized assessment tools (concept inventories) and in-depth student interviews (think-aloud protocol studies).  The presentation will highlight barriers to implementing and to sustaining reform curricula in university physics courses.