I've used it for travel around Japan last year and now I use it for Korean trip. It gives plenty of accommodation possibilities including budget ones. One may choose separate space as well as shared space. It has quite friendly interface. Important feature which places Airbnb below Booking.com (in my opinion) is uncertainty of reservation even if it is confirmed by host. In some places you can find comments as "canceled ... (few) days before arrival"
Airbnb is a website for people to rent out lodging. Founded in August 2008 and headquartered in San Francisco, California, the company is privately owned and operated by Airbnb, Inc.
Users of the site must register and create a personal online profile before using the site. Every property is associated with a host whose profile includes recommendations by other users, reviews by previous guests, as well as a response rating and private messaging system. More: en.wikipedia.org.