Couple of thoughts on Airbnb. I used it for the first time in CPH last month and we got a great deal renting a house from an awesome owner who was super nice and helpful. However I would be careful about renting in NYC as many of the rentals are illegal in apartments and their's a very small chance of you having a problem. I also don't like landlords that require security deposits in cash for short term stays. I was looking at listings in Paris that required EUR 300 deposit in cash.
Cheers
Howie