Yes, we have used our Safari card to get "priority seating" (meaning, we got priority over those waiting in stand-by)... showed up and the regular line was 1-1/2 hrs. We were seated within 30 minutes.
You either get a free appetizer or a % off your meal. You also get 10% off in the gift shop.
I would think the RFC is the same as anywhere else. And, as you have guessed, not everyone has one in their hometown so it seems pretty special.
Note that you can also use your Safari card at any of the other Landry Restaurants ... there is a Joe's Crab Shack not that far from DTD.