Liked your report! A couple of comments regarding your experience in SEL:

1) The airport is due to be relocated next year, so Kimpo is getting pretty run down (well, actually, it has always seemed pretty run down).

2) There is a good reason that the customs & immigration agents are so slow. South Korea and North Korea are still at war, and not just technically. It seems like at least once a year, the North Koreans pull something really crazy. In the past ten years, they have blown up a commercial airliner, dug tunnels under the DMZ, kidnapped South Koreans and Japanese citizens, etc., etc. If you ever return to Seoul, you will notice that the airport is ringed with watchtowers manned by vigilent Korean soldiers. The airport perimeter is ringed with a double fence and kept free of buildings and trees as well, so potential intruders will have nowhere to hide.