Like so many guests before us: We had a really good time at Stephanie's in South Harlem. The room is very nice, the bed very comfortable, private bathroom, very pleasant, and the fully equipped kitchen can be shared.
Stepahnie herself and her family have welcomed us warmly. She was always responsive to us, gave us great tips and was very relaxed.
The location is great, you almost feel like a New Yorker ;) You have exciting Harlem to the north, Columbia Campus and Mornigside Heights and Park to the west and just a few meters to the south Central Park. But clearly, if you want to feel like you're on the Upper East Side, you're in the wrong place :)
Getting around is so easy, subways 2 and 3 (express to Midtown), as well as B and C are within walking distance.