This is a 5-star hostel! The manager Mr. Yoo was very kind and gave a good overview of what to do and where to eat. The place was very clean, the ambiance was very cozy (lovely rooms and common areas), and the breakfast was good (toast and coffee/tea). The location was excellent, as it was only 3-5 minutes walk from the intercity bus terminal, 10 minutes from the tourist market, and 1 minute from the bus stop to and from Seoraksan.
The only problem I had was my bed. It was a hard spring mattress and, as a side sleeper, I had difficulty sleeping the first night (the second night was better--I was so tired from hiking!). I think there are rooms with foam mattresses, and you can ask for those in advance.
Overall, highly recommended. I'd stay again if I can get a foam mattress. Make sure to check in before 11:30pm though since the front desk closes by then.