We stayed at Jack's place in December, on quite a hot day. The outside temperature actually cooled down to 18 degrees in the evening, however the apartment stayed extremely hot all night. We found the temperature in the apartment unbearably hot, and were unable to sleep due to this. There are no windows in the apartment, only 2 sets of sliding doors. 1 set of doors opens directly to the main road, so these cannot be opened to provide venilation. Opening the balcony doors at night time let in mosquitos (we got eaten alive!), so they cannot be opened anyway. One fan was provided, but at least three fans are needed for this apartment - one for each bedroom, and one for the living area.
There is no privacy in either bedroom - 1st bedroom is also a corridor to the front door. 2nd bedroom has no windows, only shutters which open to the kitchen, and the shutters have gaps in them. Therefore if someone is standing in the kitchen they can see anyone in the bedroom. Noise travels throughout the apartment so cannot use the bathroom or have a conversation without the entire apartment hearing.
I honestly don't understand how an apartment like this was ever built, as the layout of it is awful!
The location is good for accessing Darling Harbour. It would probably be fine for a solo traveller as long as the weather is cool at the time of the visit.