We had a truly enjoyable stay at David's place and would recommend anyone interested in visiting New York to follow suit. The instructions he and Kate had left for us were precise and easy to follow.
The neighbourhood is quite safe, pleasant and not overly loud. Sometimes we could vaguely hear the subway train passing in the distance over the Roosevelt avenue, and an occasional plane would overfly us from time to time. Subway stations on the 52nd and 61st street are both five minutes away on foot and there are many markets and restaurants close-by.
We met David and Kate, but only briefly. However, we all felt very welcome in their house and experienced no real problems during our stay.