We've stayed at the Westin several times and found the rooms and service excellent. It is a great base for seeing the rest of the city. If you're concerned about breakfast, the best weekday option is to walk out the hotel onto Pitt Street, cross the road and walk up the little alley (Rowe Street) into the foodcourt at the bottom of the MLC Centre.
A great array of high quality choices for both food and drink. Deli Ziosa makes the best espresso/cappucino/latte, and there is a fruit/yogurt place which mixes a delicious passionfruit yogurt.