I've attempted to stay at an AirBnB several times. It definitely feels like a niche market. I use it because I think it's cheaper. But, people on AirBnB(the ones that seem safe) seem to charge regular hotel rates that I end up choosing a hostel instead.

Occasionally you find some hidden treasures and friends of mine have reported having an entire apartment to themselves in NYC for a fraction of the cost of a hotel.