Great location, clean and efficient, comfortable, quiet... really great stay.
As other reviews have said, the taco place on the corner is great (barbacoa tacos), it's about two blocks from the Q line which was perfect as I was headed to Carnegie Hall just about every day. A few blocks away is Le Reveil, which was my favorite coffee place in Manhattan for the 5 days I was there... lovely pastries and excellent coffee.
The place itself is remarkably quiet for Manhattan. As another reviewer said, the heat pipes do make a noise on occasion, which is startling the first time if you're in bed, but not a problem. There's almost no street noise heard in the apartment, and the neighborhood is quiet and safe. The apartment was clean and Mary and Denise were extremely quick in their responses.
There are plenty of stairs in a narrow staircase, so if you've got heavy suitcases or issues with steps, that might be an issue... but then again, that's likely to be a problem well before you get to the apartment in NY. Everything worked out very well and I'd happily stay here again!