I loved staying at Karin's place. Karin, her husband and some friends who live there are all very nice people and welcoming.
The room is small but comfy and clean and there was everything I needed. The shared bathroom with the other people on the floor is super-clean and I could use it whenever I wanted.
The house is right next to Morningside Park and Columbia University (absolutely perfect if you have to do something there- just hike up the park!) and close to busses and subway.
I absolutely enjoyed my stay at Karin's and I will book this location again when I'm back in NYC.