We had an interesting tour guide, and therefore we enjoyed the tour. The itinerary itself is not very exciting without JSA, there was also quite a bit of waiting around time at many of the stops. The third tunnel was a real workout, both the incline and the fact that the clearance is very low, so you are climbing all bent out of shape with a hard hat on.
Seoul itself is a nice city, we were there for a few days, there are a bunch of palaces and gardens, one of them has daily changing of the guards and lively markets and shopping streets around town.
Having been to Japan 4 times, and finally reach Korea 6 months ago, it sure was nice change of pace.