As JNelson113 says, Rim Rock Café has a great reputation. So do BearFoot Bistro and The Edgewater (unique location). Not inexpensive, however.

I find prices very high in Whistler overall and sometimes the service or quality is a bit spotty at the mid-level restaurants. I thought the Westin itself had OK food, but a limited menu.

The Westin staff are very good and they will have lots of information on dining options. Browse sites such as:
http://www.whistler.com/whistlerlife/restaurants/

Be sure to try and get one of the one bedroom suites at the Westin rather than a Junior Studio. I really found the studio suite claustrophobic and noticed noise from an adjacent suite. The other couple of times we stayed there we had a one-bedroom suite and it felt more spacious. I think your view choices are golf, mountain and forest. We were happy with the forest view from the 9th floor of the West Tower with a small balcony, although we did notice continuous fan or vent noise in our bathroom (maybe because the rooftop ventilation is right above?). The East Tower has the lovely Mountain Suites on the upper floors, but they were beyond our price range!

The Westin Whistler has its own web site with detailed layouts of the room types and other information.

http://www.westinwhistler.net