I have rented and hosted on AirBnB for over a decade, and it was one of the main tools we used when I worked for a vacation rental company. I have rented out my own home as well as managed the rental of multiple other properties.
Guests: AirBnB can be a good resource for guests provided they realize it takes more time and effort than booking a hotel. You can both save money and have a better lodging, in a better neighborhood, with a kitchen and sometimes interaction with a local host, if that's your thing. You will probably have a positive experience with renting on AirBnB, provided you:
*Do Not rent from a host with no reviews. Note, some listings have no reviews, but if the host has positive reviews for other properties, chances are they've underpriced their new listing to attract it's first guests and you may get a good deal.
*read the reviews with a jaundiced eye. Most Americans feel intense pressure to be polite in their reviews, and will soften negative feedback. If reviews mention the place had "some noise" and "could have been cleaner", realize it's a dump located directly under a freeway overpass. Most rentals are clean, safe and run by hosts who care, so you'll still find plenty of highly reviewed places without red flags.
*Consider VRBO and homeaway as well - their fees are lower.
Hosts: my advice: Do not list only with AirBnB. The main issue with the company is that they occasionally suspend or terminate host's listings without any notice, warning, or reasons given. It's incredible frustrating, and, if you are counting on AirBnB for some of your income, can really mess you up. They recently suspended my (5 star, 8 year old, suprhost) listing without notice and will not tell me the reason, the result, or give me any timeline about resolution. The only way I knew my listing was turned off was that I happened to go onto AirBnB.com one day to update some of the listing details. It took me several days of repeated calls and emails to be able to speak to their customer service people, who told me "I don't handle this type of case, I can't forward you to the people who do. You just have to wait by the phone for them to contact you." And promised me I'd hear from them. Weeks later, I have heard nothing. I know several other hosts to whom this has also happened.
When it works, AirBnB is a fairly well designed tool, but I highly recommend also listing with VRBO, hHomeaway or other sites, so you aren't hamstrung when AirBnB drops the ball.