What makes Jongmyo Shrine special is it's unique architecture and peacefulness. The site is a splendid place to take a walk, or as a quite spot for reflection. This site will not amaze you, but be patient and relax and you can certainly appreciate this beautiful shrine.
Update: I revisited Jongmyo in 2016 to improve my pictures and better appreciate this quite WHS. My second visit was rewarded with a serene environment and lush green landscapes in the center of old Seoul. A pleasant 45 minutes deviation from my rather full itinerary. I've noticed some nice changes to the surrounding property since 2008. The entrance has been expanded forming a "green axis" that is aimed toward connecting Jongmyo Shrine with Namsan Park. I am excited by this development. In the years to come, Seoul City Wall, Changdeokgung Palace, Jongmyo Shrine, Namsan Park, Yongsan, and the Han River will all be connected. It is astonishing that this "green axis" will happen in a city of 10 million.