This is an often over-looked stop by people in the area. The Dam is beautiful, and there is an opportunity to learn a lot about Vancouver's water supply. Also, it's a quick, but worthwhile, stop of you are coming from Grouse Mountain, or Lynn Canyon.
This is an infrequently visited, and therefore, relaxing, stop. There's also a nice park in the area, and it would be a great place to relax after a busy day. If you need to get away from people, but still want to do some sight-seeing, this is a fantastic stop.
Try the water in the fountain. It tastes delightful.