Coming a little late to the game here with this comment, but I live in NYC and my wife and I have hosted several couchsurfers from couchsurfing.org. Every time it has been a great experience. Usually it is couples looking for somewhere to stay, and feeling more comfortable staying with another couple. They've come, done their tourist thing, hung out with us, and provided us great stories about their travels and experiences, and even cooked us dinner once or twice. Usually our only worry is giving them a key to our apartment, so we only do that if we trust them after a day or two, or they have good references.
We host couch surfers because we have traveled a good amount and we know how much better your trip is when you get to meet and hang out with the locals. We also expect to take advantage of couchsurfing when we travel next, and so we feel it is only fair that we host others. On top of that we know how expensive it is to stay in NYC! Hosting someone here really saves them a *lot* of money :)
I highly recommend hosting a couchsurfer if you can, expect to learn a lot about different parts of the world, and to make some new friends.