Do you have any advice for potential travellers?
The general concensus is that the trip is best done from Joburg to Cape Town, which is a great place to end up in. My one real regret is that I didn't add on some extra time there at the end of the trip - there wasn't enough time to cover everything that I wanted to see and do, and Cape Town is a very cool city where it would be good to spend a few days after the trip ends. I would definitely recommend doing so.
Travel light - there are plenty of opportunities to get laundry done easily and cheaply [notably Bilene in Mozambique and Lesotho] and it is unnecessary to haul around a large and heavy bag. A lot of the hotel/guest house accommodation is on first floors, and it is so much better if you can carry your own bag up and down the stairs.
Don't be put off by the camping - most of the campsites are in stunning locations, and it really is the best way to enjoy the landscape. The tents are put up and taken down for you, and the beds are really comfortable. Similarly, don't be put off by the thought of a day of walking in the Drakensberg. The gorge walk passes through amazing scenery and is really not to be missed - although it ascends gradually on the way there, it is mostly contouring, and there isn't a huge gain in height, so not particularly strenuous.
Finally, as the trip notes say, there are some long driving days. But they are a necessary part of covering all the ground and seeing different places, and are usually enjoyable in their own right because of the ever changing scenery that you are passing through, and the one-off spots - baboons, antelope and mountain zebra by the roadside and the people and villages that you pass by. There are plenty of coffee/toilet/leg stretching stops. Sit back and enjoy it, take an iPod to listen to and a book for the rare occasions when you don't want to just sit and take in the scenery.