While I have no experience with the product, I can research for you if you have any particular question. This posting seems to be out of place, maybe mod can move it to http://www.flyertalk.com/forum/asia-460/ ?
I do not believe ktx serves ICN airport yet, so you'll need an alternate ground transportation to a train station in Seoul if you are flying in.
If you are curious about general experience, have you tried google search?