Pros
Good salary for a grad student. Everyone here is on a fellowship, so you're guaranteed funding for 5 years. There are good benefits. We have decent health and dental insurance. We also have insanely subsidized housing. Manhattan rent for less than $800 per month. There are even some good perks. The university provides computers and discretionary research spending money for all students. The Dean's office really cares about the students and do their best to help us. There is also a minimum of administrative red tape and departmental requirements: no quals, not too many required classes.
Cons
Each lab has a unique culture. There are some in which the PI can be very demanding and on top of the grad students and some in which you will barely see them at all. Joining a bad lab can really affect your experience.