This very scenic video shows the early weekend ride from Rushcutters Bay to Darling Harbour using the Cahill Expressway shared path.
The views from the shared path above Circular Quay are really good and you are a long ways a way from the crowds. Unfortunately you soon will come across a few runners and not much space and some steps. Still its an interesting adventure as the video shows.
Find the Cahill Expressway Shared path on the Sydney Map here >>>