Another one of my favourite places. I confess that I can often be found here having lunch after a night of over imbibing. The mandu soon tubu chigae (dumpling tofu stew) always seems to set me right again. Lots of great side dishes, as is typical of Korean cuisine. And to get out of there paying as little as you do has to make any budget-conscious diner happy.
I lived in Korea for several years (not Seoul, I was out in the sticks) and I can tell you that the food and the atmosphere are the real thing. It's really like stepping into Korea for a while: it's crowded and busy, but great.
All of the chigae (stews or soups) are great, but definitely try the dol-sot bibimbap (mixed rice in a very hot stone bowl) -- one of my favourites.
BTW when they bring you the egg, you can just crack it yourself and put it in the soup. And when they pour water into the stone bowl containing the remainder of your rice, that's dessert. :)