Stayed at the HI Sandton in November for one night - about 730 rand if I recall correctly. PC points didn't post and still haven't despite putting in a missing points request.
The property is brand new and very nice lobby. Rooms are excellent. Property lacks any kind of character - but I think that is common with the Sandton area. Free parking for all guests. About a 5 minute walk from Nelson Mandela square, with a smaller mall right next door. Concierge tried to dissuade us from walking to Mandela square due to safety concerns: I don't think this was out of vested interest to take hotel car but rather a common advisory. In any case, during daytime I don't see why one wouldn't walk as there are many people and the area is very commercial with lots of people about.
Internet is expensive, and no perks for platinum status whatsoever. But staff was very nice and helpful. Pool was advertised as open but had no water in it, although a lifeguard was on duty and towels were provided.