Night skiing and a quality ski school program
Horrible parking, horrible base layout, crowds
Keystone was a great mountain- 20 years ago. However, since Vail's involvement with the area, it has turned into a real mess for the day skier. They have built the base out with condos and other "village" stuff, which creates a half-mile hike to parking. Sure, a lot of resorts do this, but they also have shuttle service that drops you off right in front of the lift. NOT KEYSTONE. Expect to start and end your day hiking with all your gear.
The second mess is the River Run base area. I really want to know who designed Keystone so that the main base area is served solely by a relatively steep and long blue run. This run is subsequently overused, has the snow scrubbed off of it by 11:00 AM, and is always full of skiers skiing way beyond their ability trying to make it to the base. Recommendations are to use the Mountain House Base (if you can find parking and a spot there). Alternatively, stay away from the base. Ride the gondola to the top, ski other lifts, then download on the gondola at the end of the day. Especially recommended if anybody in your group is not a proficient skier on a steep, snowpacked (or worse) grade.
North Peak is a fun mountain for fast cruisers, and moguls. The Outback has good gladed terrain for both blue and black skiers, but the lift is typically JAMMED.
The Packsaddle bowl on the far right used to be an excellent place for beginner skiers. It has since been turned into a GIANT terrain park. Not sure how I feel about this. The terrian park looks epic, but I had lots of fond memories of learning to ski there, and later teaching tons of kids the art of skiing there as well.
Keystone is not a bad mountain, but all the hassles can easily make for a bad experience, and that is why I would recommend skiing elsewhere. After all, Arapahoe Basin is just up the road.