Poor communication: I got a text from a third-party service about picking up the key, no instructions for anything in the apartment (including where to put trash etc), and then didn't hear from the host until 6 am the morning of checkout, saying we wouldn't be able to contact him further because his phone had been stolen. Fortunately we managed to figure things out on our own.
However, four days after we left, the host filed a fraudulent claim saying I had broken into his storage closet, which was a complete and utter shock—and completely untrue. I've always had good experiences with Airbnb and don't like leaving negative reviews unless it's absolutely necessary, but he is not reliable or trustworthy, and I would strongly recommend finding someone else to rent from.