I learned through experience— It's one thing to use AirBnB to book a weekend away, and it's another to show up in a foreign country jetlagged and have nowhere else to go at 6am in the morning.
I warn people using AirBnB to ask lots of questions before they book in a foreign country. Don't believe the reviews on the AirBnB site. I had a bad experience with a well reviewed host. And now I can't leave a review about it due to a massive flaw in AirBnB's review system.
In June '12, I used AirBnB to book an apartment for two weeks in Brussels with a host named Maximillian. When we arrived exhausted at 6am, he said our original apartment had water damage and took us to an apartment in another neighborhood with almost none of the amenities that he listed. And almost no furniture. That's right, no place to put anything. No glasses to drink water from! Not even curtains on the windows. I could go on and on.
To make matters worse, AirBnb will not allow me to leave a review to warn others because I cancelled my reservation with Max and left after 4 days. Even though I still had to pay for those days. It's a flaw with the AirBnB and one that everyone should be aware of.