Marriott's are pretty good about recognzing stuff like honeymoons, so you may have some luck by dropping that info.

As mentioned the hotel is not right on the harbour, and there are a bunch of tall office bldgs and hotels. On my stay there in November I had a room that had a partial harbour view, which was towards the bridge (vs. opera house).

As stated ... the higher you are, the better chance of getting great views. Even though it's your honeymoon, the city will be great to roam around and see the views close up.

Congrats as well.