Sorry for the late reply to this thread. On one of my recent trips arriving at ICN I decided to take the train. I'd already figured it would be slower and much more inconvenient for me than taking a bus directly to my house or office, but I had some spare time so wanted to try it out. After a fairly long walk to the train I unpleasantly discovered the ridiculous price of an express train ticket (almost 8,000 KRW) and refused and went back to get a bus. I don't see how they'll get many customers with such outrageous pricing and then only going to Kimpo. I've never taken the bus to Kimpo, but taking my bus that is at least twice that far is only 8,000 KRW. Add the walking time to get to/from the train and it just isn't practical for travelers to take the train. I think the only customers they'll likely see are airport workers who commute everyday and might be able to save a little bit by taking the normal train. Looks like a white elephant in the making to me.