District- and state-level efforts to remake teacher evaluation systems are among the most substantial and widely adopted reforms that U.S. public schools have experienced in decades. Research on these next generation of evaluation systems has focused overwhelmingly on policy goals, program designs, and performance measures. However, still very little is known about how these policies are interpreted and enacted by school leaders. In this study, the authors examine the perspectives and experiences of principals as evaluators in a large urban school district in the northeastern United States that recently implemented sweeping reforms to its teacher evaluation system. The study focuses on principals' perspectives and experiences with classroom observation and feedback because this process is a primary mechanism through which evaluation is intended to promote teacher development. Principals' abilities to rate teachers accurately, to facilitate teachers' own self-reflection, to make specific actionable recommendations, and to communicate this feedback effectively are central to any evaluation process intended to improve instruction. The district studied is an urban district in the northeast that serves a racially and linguistically diverse student population. Interviews were conducted with principals lasting 45 to 60 minutes in July and August of 2013, the summer after the first year the new evaluation system was implemented district-wide. It was found that the quality of feedback teachers receive through the evaluation process depends critically on the time and training evaluators have to provide individualized and actionable feedback. Districts that task principals with primary responsibility for conducting observation and feedback cycles must attend to the many implementation challenges associated with this approach in order for next-generation evaluation systems to successfully promote teacher development. A table is appended. [SREE documents are structured abstracts of SREE conference symposium, panel, and paper or poster submissions.]