My albeit limited (in the sense that was essentially all I did in Korea) experience was phenominal. I think the best part (with all due respects to my family, friends, and students whom I left behind) was to be a total student-to immerse myself totally into the training.
The experience was incredible on so many levels: social-I got to meet other students of black belt ranks from 1-7th from all over the world. We stayed after the day's instruction was over and worked out together and helped each other. At the end of the course the Kukkiwon sponsored a luncheon at a hotel.
It was incredible from a historical perspective: I had an essentially personal tour of the Kukkiwon Museum which is located just above the cafeteria on the grounds. No one else was in the Musuem and the curator (whose name I have unfortunately forgotten) was so happy to allow me as much time as I desired to walk through and observe 50+ years of TKD history. He gave me a Kukkiwon souvenir as I was leaving.
It was incredible from a tourist's perspective: I walked every day from my hotel to the Kukkiwon. I took different paths and saw different sights. I rode the subway to Dongdaemun where I shopped for souveniars at what I understand is the largest outdoor marketplace in Asia.

Got a belt embroidered by MooSoolSa while I was there-all done in about 10 minutes!
It was incredible from a training perspective: as a student, I got to train with the Kukkiwon Academy's instructor, GM Lee, Chong Kwan. He's the model performing the poomsae in the Kukkiwon's videos (which are on the website). We went over everything from basic techniques, to advance techniques, to poomsae, to applications.I learned about the history of the art, the history of some of the art's prominent instructors, and the various types of instructors, how to create and manage a curriculum. I got to watch the Kukkiwon demonstration teach coached by the incredible Grandmaster Lee, Kyu Hyong. I got to train with and spar with the Samsung professional team and the Korean Olympic team-received encouragement from Coach Kim, Sei Hyuk.It was invigorating mentally as well as physically!
Could I have received the same training in the US? Sure, there have been Foreign Instructor Courses outside of Korea.
Would it have had the same positive impact upon me? No way.
Would I to to Korea again? In a heartbeat.
Miles