I've been using airbnb very frequently since Jan 2012, both as a superhost and as a guest. This is the most frustrating experience I had so far.
I booked to stay at Ian's place from Sept 19 to Sept 25. But I didn't receive my visa on time. So I have to postpone my trip to Sept 22. I understand Ian has a strict cancellation policy, I didn't expect to get any money back. I just would like to check in on Sept 22 instead of Sept 19. Ian said he won't be there to give the keys to me on Sept 22, and then refuse to consider other options. He would reply "Regret it is not something i do". I asked airbnb support to help, but they said Ian is unopen to mediation.
So as a result, even though I paid for Sept 19 to Sept 25, and arrives on Sept 22, I cannot stay from Sept 22 to Sept 25. I could not get any money back either.
Keep this in mind when you do your booking, it is better to consider hotels or other listings which have flexible cancellation policy if you are not 100% sure you are going to make it on time.