I gave them a call yesterday to see what the hold up is. They are the last school I'm waiting for, and they've had my application since the end of November. Basically, if they haven't responded and you applied early on, it means that they reviewed your file once, and are now comparing you to the applicants who applied towards the end of the cycle. She said that they expect to be done by the April 15th deadline, but that their could be some applicants who receive their letters as late as the end of April. Hope it helps.