Why is it that most good pho houses are in sketchy neighborhoods? Kangnam is no different. Though I've never had problems, I would recommend bringing a friend.
That being said, I love the pho here. It is consistently good, with the beef being on the lean side for you calorie counters. My favorite is the #10, or pho with brisket only (not a huge fan of the tendon and tripe). For something sweet, don't miss the sweet bean drinks. The beans are truly that...sweet.