Sun Valley has the runs! The mountain has lots of steep runs that keep going steep for a long time. This means that there are a lot of good skiers and boarders on this hill. Not much in the extreme beginner runs, but if you can get down the hill, you will have plenty of great terrain. Many runs are covered by fancy, state-of-the-art snowmaking, so the snow is great most of the year. Many runs are groomed nightly by a fleet of snow cats, that really make the snow nice. Lots of high speed, detachable quads, and no lift lines, so you will get up the hill fast. Great restaurants on the mountain that are a cut above most ski areas. Did I mention that it is never crowded?
The apres ski scene is not the greatest. The local bars don't hire nationwide talent, but they still seem to pack the small dance floors. The town at the base of the lifts is Ketcum, where most of the resaruants and bars are located. Sun Valley city itself is a mile away, and the night life there is mostly jazz clasics in vintage opulent decor.
Large variety of great restaurants in Sun Valley and the nearby towns of Ketcum and Hailey. There are hotels in each town as well. Hailey is 12 miles from the ski hill, and so has cheaper services, but comuting to the ski hill will be in rush hour traffic.
This resort is not cheap, but you get a lot for your dollar. Lots of movie stars and extremely wealthy folks have vacation homes in the area, so there are a lot of upscale support businesses available.