We stayed for a week and had a really nice time.
The apartment is very modern and plenty of space (we were two but it is more then enough for 4).
Marcus is super responsive and takes care of any question or concern.
The location is convenient; it takes a 40min walk to the Opera House / Circular Quay, but almost half of it can be done through the botanical garden - best way is to enter at the Marina through the stairs, up to the walkway behind the buildings; maybe the google link helps to find the best entrance and walk:
https://goo.gl/maps/73ddfvyTqkR2
In summary: we had a great time!