Pros: Great fall line runs, excellent lift system, first-class infrastructure
Cons: snowfall can be sketchy, expensive, relatively remote,
Sun Valley doesn't need much of an introduction. The classic profile of Baldy from the River Run side is as recognizable as the profile of Lone Peak, that barn in Steamboat, or the tram docking at Snowbird or Jackson. Baldy is a beautiful natural ski mountain: it's 3400 feet of nothing but fall line on several aspects, with some south- and east-facing bowls.
The layout of Sun Valley may seem a little confusing if you've never been before, but it's not really that complicated. The incorporated resort town of Sun Valley--the original resort--is a couple miles east of the town of Ketchum; and Bald Mountain (the main "Sun Valley ski area") is just on the western edge of Ketchum. (In fact, Ketchum is one of a very few places in the U.S. where lifts that serve a major mountain run right from the edge of town.) Dollar Mountain, a ~600 vertical foot, treeless, dedicated teaching mountain, is between the town of Sun Valley and the town of Ketchum.
Sun Valley takes pains to create a smooth, no-hassle ski experience. The lifts are modern, fast, and well located. The on-mountain facilities are all brass, hardwood, and subtle refinement -- in other words, the on-mountain restaurants smell more like money than corn dogs.
The mountain has one of the skimpiest annual average snowfall totals of any major ski area in the Rockies, but they make a lot of snow and groom it constantly. One side benefit is that, if there is a major dump, you can put together these long, thigh-burning powder and chop runs through 3000+ vertical feet of perfectly smooth and consistent fall line terrain.
The place is always uncrowded due to its remote location, and although the skiing can be challenging to an advanced skier, there is nothing extreme on the mountain.
Sun Valley resort is shot through with a certain type of glitzy history. There are pictures in the lodge that capture festive moments from days gone by: Gary Cooper tossing olives into Hemingway's mouth during a cocktail party (not that there's anything wrong with that), shirtless dandies from the 30s working on their melanomas on the sunlit slopes of Dollar mountain, and similar Hollywood-goes-to-the-Sawtooths vignettes from the golden age of film.
One thing that makes Sun Valley so appealing is how comfortably the history nestles in alongside the modern lifts, grooming, and amenities.