Any of the rooms facing the Harbour are great. However the upper levels obviously give you a better view of Darling Harbour. This hotel is one of the best in the Accor network
Basically all the rooms on the harbour side will have a good view. The first time I was upgraded to the top floor suite which was very good.
Beat views are the Darling Harbour view-above floor 2 and starting ending with 12 and upwards
hope that helps