Sandton Inn Inanda was a lovely place to stay. The staff are very nice and accommodating, the breakfasts are pleasant, the grounds are beautiful, and the price is good.
If you're just there for vacation and are renting a car, this place would be ideal.
If I have any reservations about staying there again, it is on logistical grounds. I was in Sandton for business at a conference center in Nelson Mandela Square, and the inn is tucked away in the Inanda neighborhood. In any Western City the 3 km of distance would be a lovely little walk; in the Sandton neighborhood of Johannesburg this is technically possible but unadvisable - there are barely sidewalks, putting one at the mercy of car services. Fortunately I found these mostly reliable, but it was still a pain to get around because phone service is spotty. Because of this, if I go to Sandton for work again I will likely stay in more expensive lodging near the city center, which will still be a deal if I'm not paying for car services.