The restaurant at the top of the Sydney AMP Tower is a great way to see the city and is a better value than many tower restaurants. The all-you-can eat lunch buffet provides a wide variety of choices ranging from cold seafood to roasts to Asian dishes to lovely desserts. The food isn't outstanding, but it lets you avoid having to make choices and has something for everyone.
The view from the rotating restaurant is the star. Giving 360-degree views of the city, it's a great way to get a sense of what is where. One of the highlights for me was the terrific view of the Olympic stadium.
Entrance to the restaurant is through a shopping mall. Signs to it aren't terribly helpful, guiding you to the podium level without explaining where that is. Ask in one of the stores (some of which are very nice).