This was a ski trip with eight people. We picked Sun Valley because we had a friend living there (though there are certainly other good reasons to go there). The group stayed in a condo in Elkhorn.
The main event was the skiing. I enjoyed it a lot. In fact, I came back to ski here again a number of times since this trip. One great thing is that it's easy to rack up the vertical at Bald Mountain. The Warm Springs high-speed quad runs pretty much from the bottom-to-top, over 3,000 feet. Most weekdays, you can easily exceed 10,000 vertical per hour here. The runs are steep, fast, and long.
My favorite skiing here is to follow the sun all day, starting with River Run and/or Christmas Ridge, then Seattle Ridge (the beautiful lodge here is the place to have lunch), and then over to Warm Springs. Sun is pretty common, and the weather is often great...the mountain has loads of fun steep groomed (or sometimes groomed) runs. It is drier here than places like Colorado, though, so powder-hounds will have to rely on a well-timed storm.
Ketchum is a very fun town, with many more great dining options than you would expect in a town its size. Some recommendations: Pioneer saloon - highly recommend it...great steaks, potatoes, etc., fun and festive Grumpy's - watering-hole/shack with tasty burgers Desperado's - solid, basic sit-down Mexican Rico's Pizzeria - i think they discontinued their delivery (check on it), but you can do take & bake (they partially cook it) Sushi on Second.
Those looking for other activities aside from downhill skiing...options include cross-country skiing, snowmobiling, ice skating (at the Sun Valley Lodge), and live skating performances (some big names typically).