Driving, train or sneaking a ride on the NYU shuttle? I don't know about NSUH to the city but I commuted for 6 weeks (cushy OB rotation) from Brooklyn to NSUH and it was a pretty decent commute. Probably took me 45-50 minutes door-to-door by car.
I did drive into the city several times via the Queens-Midtown Tunnel and it was probably 30 min to midtown on a good day. I can imagine that it's 30 min to the city by car or sneaking a ride on the NYU shuttle. At the time I was there, you had to have an NYU ID to get on the bus, a North Shore ID wouldn't cut it. After hours is a different story of course since the shuttle stops running at 5 (NYU students never showed up before 7am and had to leave by 4:45pm b/c of the shuttle).
If you're trying to catch public transportation, count on 2 hours each way...I took the train once and it took almost 90 minutes just to get to Grand Central.