Melinda, I find AirBnB's payment system ideal. Within the past 2 months I've had five guests. Tomorrow a sixth will arrive, I have six more booked for March, April, and June.
I think the benefit is threefold: If a guest needs to pay AirBnB upfront, it strengthens the commitment to show up; no cash needs to change hands; and the money is transferred within 24 hours of the guest's arrival. I use PayPal. and have had no problem.
And because my cancellation policy is strict, even if a guest cancelled I would still be able to retain a decent portion of the fee. And if a guest ever requested a partial refund (or full refund in the case of an extreme emergency, for instance), he/she would simply take it up with AirBnB. And in the meantime, those days that the guest had cancelled would be free again for another guest to book.