If you prefer to eat before and sleep on the flight (definately recommended for the later departure from JNB), skip the food in the lounge and eat at the African Cafe. Definately worth paying for the far superior food.

When timing your connections, bear in mind there is a fair walk in JNB between int'l (terminal B) and domestic (terminal A), plus there is a good chance of a bus. I've made 60-min connections but it has been very tight.