If you are referring to the Augrabies Ultra in the Kalahari, I haven't run this myself, but I know plenty of people who have (and who have raved about it), and I also know the organisers (who are welcoming and supportive).
I've heard nothing but good things about it. It does have smaller fields than the MdS (dozens rather than hundreds), without the media circus and profile that follows it. Mimi Anderson, who is one of the UK's most experienced ultra runners often says that it's her favourite race in the world.