Good Sam is a whole bunch of things.
Gas discounts at Pilot/Flying-J
Discounts at Camping world
Discounts at some campgrounds (Just saved about 25 bucks making a reservation for my last 5 nights in SC this spring)
Other discounts. NOTE that one reservation paid a year's membership
There is also Good Sam's Roadside assistance. It is a "prepaied" service like Coahnet and AAA sine I've never used it I can say no more.. I have used the roadside rider on my regular insurance (I pay they pay me back).
Good sams also has a "Breakdown Insurance" Once your dedutable is met they pay the rest of the repair.. I am not convinced it is worth it (and i had it for a year.. but that was a special year).
They have other services too.. The only ones I'd consider are Membership and roadside.