I have stayed at the Westin over 75 times (for business) and like the hotel very much. It is handy to the business and shopping areas of Sydney. I have found the staff very helpful; but of course they recognise me from my visits to the hotel.
Breakfast at Mosaic is excellent; but on this stay I had a room-only rate so ate at the Executive Club. Breakfast there is pretty ordinary with a small selection of food and the toasters take a long time. Food at Mosaic has been good but on this stay I felt that the menu was not as good as it previously has been. There are a number of restaurants downstairs in the same building and also plenty of cheaper choices close by.
I stay in a tower room, which is very modern. The heritage rooms are quite pretty and are done in a more traditional style; but I always like the clean, modern look. The rooms are clean, neat and the bathrooms are good (I like to read in the bath).
The price of the hotel can vary greatly depending on the time of the year and can vary from competitive to quite pricey (but all of the 5 star hotels in Sydney are the same). Prices at the bar are quite high--for example they are more expensive than the Hyatt on Sydney harbour which is a very high-class hotel.