The Johannesburg Zoo seems to have a good reputation when it comes to looking after the welfare of the animals they have, proof is the wide enclosures for the bigger animals to roam around (of course one can't compare this size to the animals' natural habitat), plus the animals in the zoo look healthy.
Compared to other zoos in most cities, the Joburg zoo is spacious at 81 hectares. The zoo has lions, elephants, giraffe, zebra, monkeys among others which seem to enjoy their environment compared to their friends who have been transported and stuck in a 15ha zoo in a European city. I couldn't say the same for the polar bear or the seals though. It's a well looked after area for families to spend the day and I prefer this over going to a mall. It's a convenient place to go since it's very close to where we used to live.
I also like to fact that kids are forced to walk (if parents are not bullied into getting one of those fancy schmancy push carts displayed next to the rides!) thus expending their energy that would hopefully lead to a good night sleep. The Joburg zoo is clean in general, I haven't used their w/c facilities so I couldn't give a fair comment to this. Overall, a good place to bring the kids along for a day out.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.