I think it is where you get the gas prices. It is updated weekly. The navigation stuff is updated a lot less often.
When I needed the phone number for the FBO where I had parked my plane, I pulled out my ipad, selected airports, then I clicked FBOs, and I immediately found the phone number. It was a big help.
As for the paid advertising, I think that's a small part of it, and it isn't bad. For example, try KSUS, which is a big GA airport near St. Louis. Atop the list there's a colorful ad for TAC Air, followed by the usual less flashy listings for the other FBOs.