Yeah my old property manager used Appfolio. They didn't charge a fee back then but I heard that they started doing to about a year or so ago. I would pay the extra $2 though rather than get dressed and drive across town to pay my rent. I also liked being able to make maintenance requests online and upload pictures with it so the maintenance guy knew what he was getting into ahead of time and could bring the right tools or parts. 

Maintenance at my current apartment building is abysmal. I've had no running water in my kitchen for several days and the maintenance guy's tools are all over my kitchen floor.