Sun Valley isn't just a hill and a bunch of condos like so many other western resorts have become. It's really one great big all encompassing experience. The history, the ambiance, the culture, the skiing! Everything! It's great!
If you want a great vacation experience, this is the spot. However, if you desperately need scary steeps, you might opt for Jackson Hole or Snowmass. Still though, not much can beat having the town literally cradle this mountain. It is absolutely picture perfect. No major freeways to bring all the crowds in (in the winter, the road pretty much stops with Sun Valley), most of downtown retains its historic architecture. Some of this is being ruined by a lot of new development, but overall the charm has not been lost.
Dollar mountain really is the best teaching hill in the world. Great beginner terrain. The only downside is it is disconnected from Baldy.
The hill has endless vertical, a great uphill lift capacity that hardly ever sees lift lines, and excellent groomers.
The downsides? Snowfall and lack of very challenging terrain. Sun Valley is parched compared to every other resort of its caliber (only 220 inches annually), which they have compensated with a great snowmaking system, but it just can't beat the real thing, and snowmaking terrain is highly limited to a few trails. There are also no really scary steeps here. The burn off of the top however might be the most interesting skiing experience you could have at any resort right now. The Castle rock fire burned thousands of acres off Baldy's backside, and now all the trees are scorched black sentinals that ski better than any aspens if you get the snowfall.