Terrible experience.
I had a month-long reservation and arrived to LA at 4pm on the day of my check-in. When my flight landed, I texted Denise to get the information for the lockbox. On the listing, all that was written for check-in instructions was "lockbox". In my experience, hosts often don't like to send lockbox codes out until the previous guest vacates, so I wasn't too worried that I hadn't received any check-in information when my flight departed in the morning. When Denise didn't respond to my messages and phone calls, I started to get worried. I went to the apartment, but had no way to get in. After several hours waiting, I called AirBnB to cancel my reservation and give me a full refund (which they did). Luckily, I had friends in LA whom I was able to stay with that night, otherwise I could have been in a dangerous situation with no place to stay.
I FINALLY heard from Denise the next morning. She said she was "out" and that the code "didn't send." It is the host's job to make sure they are available during check-in in case there are any problems. This was inexcusable and unprofessional. I've never had something like this happen in many years of using AirBnb. I'm still working to find somewhere to stay for the month that I had planned to stay at Denise's place. This really caused me a lot of stress and inconvenience. All in all, it may have been for the best. The apartment didn't seem to be in a great area -- there was a pretty big homeless encampment just a few blocks away.