The hotel was a good place to spend the night. It has just about everything you'll need: huge screen TV with many channels, mini-fridge with a few complementary non-alcoholic beverages, microwave and extra bottles of water on the ground floor, jacuzzi bathtub, bathrobes, desktop computer with Internet, and access to a gym (I didn't try it; my understanding is that it wasn't part of the hotel but a separate business, but staying at the hotel gives you access to it).
The neighborhood has restaurants but is otherwise kind of boring. The subway can take you to Olympic Park and Chamshil quickly, and Gangnam isn't much further from Chamshil. Unfortunately, you're far away from places like Hongdae, Myeongdong, Itaewon, Jeongno, Daehangno (Hyehwa) and Yongsan.
This is how you get there from Gangdong station: Go out Exit 2 and turn right. Go straight until you see Gang Dong Seong Shim hospital, at a distance, on your right. Go towards it. Walk past the hospital, then turn right. Keep going and you should see a pink-red "Hotel Argo" sign up high.