Eating out in Whistler is as good as most major NA cities. There is so much choice and, unfortunately, not all of it is truly good food. For the top end, Araxi and Umberto's come to mind. For less expensive Italian, try Umberto's lower end Trattoria location a couple blocks away. The Westin itself has a fairly good dining room, however, I prefer Sunday brunch there over lunch or dinner.

Here are the sites:

www.araxi.com
www.umberto.com

Word of caution though - many restaurants in Whistler close for a week or longer in periods where business is slow - normally in the October/November period though.