I've flown to South Africa from Seattle on three occasions. The first two trips I flew United to Dulles and the South African Airlines to Joburg. The third time, I flew Delta to Atlanta and then on to Joburg.
South African Air was a nice flight, decent meals, but there was a refueling stop in Dakar. Apparently, Airbus planes aren't able to make the trip non-stop. Arrival and customs were no problem. Return trip on South African was the same with refueling stop and decent service.
The Delta flight, using Boeing 777's, makes the trip nonstop from Atlanta to South Africa. We did have two passengers die from heart attacks on the return leg but that wasn't Delta's fault. The crew handled those emergencies very professionally.