I for one would like to be a Plus listing if it helps my bookings and allows me to charge slightly higher prices. However, it's not going to happen because, although I meet amost every criteria, I do not have private bathrooms for my guest rooms (I have three bathrooms + an additional cloakroom/powder room between four bedrooms and no way to add a fourth bathroom).
My worry is that plus properties will be at the top of the search results, like IB, and the rest of us will disappear. I already had to switch to IB against my will because my listings all but vanished from the searches and my bookings plummeted. As soon as I switched on IB, I was busier than ever, but I can't 'switch on' Plus - not without that extra bathroom anyway...
I hope that what others have suggested above is true, i.e. that Plus properties will be targeted at the higher end of the market and probably cost more, so the regular Airbnb guests will still be booking with the rest of us.
Is there a market for Plus? Yes, I think so. Perhaps they are trying to compete with sites like onefinestay. Incidentally, one of the directors of that company was my housemate when he was still a 23-year-old launching it as a start up with a handful of other youngsters. It's incredible how well that has done, so there is obviously a market for high end home rentals.
