My experience as MSM has been overwhelmingly positive. After spending two years at a university (NYU), I realized that I was not receiving the music education on a par with a major conservatory. In addition, MSM has afforded me countless wonderful opportunities studying with a variety of people at the head of their field and professional opportunities like (as a composer) procuring commissions from professional ensembles.
Like any conservatory, study at MSM is primarily focused on one's instrument. Therefore one is expected to spend whatever gazillion hours a day practicing as one can. Coursework, especially in the music core (Theory, Ear Traning, History), is also fairly demanding, so the difficulty of balancing grades with one's major is pretty much the dilemma of any music student. That being said, GPA is less focused upon here than jury grade, which I understand is the standard at conservatories, which determines the ability of a student to return for the next year and scholarship amount. Sophomore juries are taken particularly seriously and generally seen as the "kick out" jury. But that doesn't happen too much.
As the other comment mentioned, MSM is very much a conservatory and not a university. The atmosphere is that of a music conservatory, of people traning for careers as musicians which of course carries its own tedium. There are a few alternatives, like a cross registration option with Columbia University which I plan to take part of next year.
That being said, I (as a composer) have experienced a wonderful sense of camaraderie with my fellow students and have nothing but great things to say about the performers whose quality is pretty much peerless.The school is located in uptown New York City in Morningside Heights, which is one of the safest areas of the city, slightly cloistered from the craziness of midtown and downtown, which of cousre has its ups and downs. But if you're willing to survive the 15-20 minute subway ride, everything awaits.