I visited Fritz four times on a recent trip to Seoul. Clearly I love it. It became my favourite place in Seoul. The coffee is very good (not as good as we get here in Melbourne, Australia, but that's largely due to the quality of the milk in Korea), the breads are superb and some of the pastries are excellent. Best of all, the atmosphere is buzzing.
It's a little difficult to find, and on my first visit I spent 20 minutes walking around the area searching for it (despite being able to speak and read a little Korean). My advice is to take exit 10 from the station. At the top of the escalator take a sharp right and walk down the gently sloping road, almost to the bottom. You'll see a large overhead street sign pointing left to Saechang-ro 2-gil. Fritz is down that street, on the left, right near the end.