Vantaggi
Montclair state has attracted several very good faculty researchers in both mathematics and the sciences, and the student researchers have access to better resources than one might expect from a relatively unknown university. The campus is located close to New York City and is right on the train. There is great food in Montclair itself, and downtown Montclair is great.
Svantaggi
The pay is shameful. It suggests an utter lack of respect towards the graduate students. 15k a year in the New York metro area is below poverty wage. No worker can perform their best if they don't have enough money for food and rent. Most graduate students can not live without a second job. Look into NJIT, Stevens, and Rutgers first! You can do good work here, but you had better not rely on the income.