Staying at Sarah's was great. The apartment is really nice - including a bedroom, a small kitchen with everything you need, a living room and a bathroom. The rooftop swimming pool is awesome and you can see the Harbour Bridge and the Opera while sitting in there.
Sarah was a great host. She gave us a tour through the apartment, made sure we knew how to reach her if we needed anything, she gave us directions to all the closest grocery shops and sights, she even left us some basic things like milk and granola so we had something to eat.

The apartment is in the middle of Darlinghurst 3 minutes from King's Cross and in walking distance to Oxford Street.

If you go to Sydney you should definitely stay in this area and in particular with Sarah.