the world's smartest travel social network
I've used Airbnb, with great results. (I found a wonderful rate on an apartment in Paris.) However, I did come across many listings that lacked reviews, which I would avoid -- just to be safe.
I would suggest sending a message to the owner with any questions you may have, just to get to know him a little better. Also, read Airbnb's safety policy: http://www.airbnb.co.uk/safety
Basically, if you are unsatisfied with your apartment when you arrive, you can contact Airbnb within 24 hours of check-in and request a refund.