O man i love Seoul!
I try to stop in seoul every time i'm in asia
Nice people, hot chics, excellent food... lots of things to do
(sorry i'm not too objective here, the girlfriends is Korean ;) )
Hongde and Sinchon area are my favorite (around the university) lots of bars, crazy night life, full of you crowd
I don't like itaewon, it doesn't really feel like you left the US when you're there
Enjoy it!!!