I'm no fan of booking.com, but the one thing they have is deadpan simplicity and excellent filters. Airbnb could learn some things from their user interface.
And while Airbnb may arguably employ a bit too much reliance on photos, it's the images that create much of the illusion of their earthy boutique perception. Yes, in any practical sense, it's just a booking platform like any other, but this perception is what differentiates them from the others. And it works.