Not sure why there is usually a line here.
A bit cramped and dingy to be honest. The service isn't great, and neither is the food - decent, but not worth lining up for. Most fish dishes, for example, are fried in oil. Yuk!
Authentic? For those who haven't had really authentic Korean food, perhaps. It's actually a bit more of ethnic Korean Chinese version of Korean food.
The only reason people go here, in my opinion, is the price.