I lived in Korea for 1½ years, from February of 1998 to August of 1999. It was the best experience of my life. Korea is not for everyone, and many foreigners have a miserable time there. I believe a lot depends on what expectations you bring with you, and how well you're able to cope with culture shock and leave behind your assumptions about the way things "ought to be."
The topic of living in Korea as a weigookin (foreigner) is a popular one with Korean expats. Read any discussion list about the subject, and you'll see a variety of opinions from the extremely negative to the extremely positive. Unfortunately, it's quite a polarizing issue. Those who have a negative view of the country tend to react vehemently against those who enjoyed their time in Korea, calling them apologists and accusing them of unqualified support of everything that happens in the country, including corruption and ill-treatment of foreigners (both of which are widespread). On the other hand, some people who like Korea tend to go overboard in their defense of the country, attacking anyone who points out its flaws.
This page is just about my experience in Korea, and my thoughts about the "Land of the Morning Calm."