Pros
For an employee with a permanent position, it would be one of the best places for a research scientist to be in South Korea. Your position is guaranteed until your early 60s. And great benefits If you are a college student looking for experience in research. It is a great place to learn experimental skills while earning extra cash. Spending more than one year for experience in this institute is not worth it.
Cons
KIST has Ph.D. and master programs. The wage is a little bit higher than any other graduate programs in South Korea, but most of the principal investigators in the institutions are poorly trained to give mentorships and advising. For graduate students who are pursuing their Ph.D. degree or even master's degree, would be better off to get their higher education in traditional academic institutions such as universities and colleges. Graduate students are treated as employees with a contract positions. Students usually heavy loads of administration role along with their research training tasks. For the PIs at KIST, they would need regular contractors or graduate students to run their labs. However, students are so much cheaper than the contractors, PIs are eager to recruit Ph.D. students who are likely be spending their 5 years of life. I would recommend prospect students who are interested in getting Ph.D. training to go to other universities. Look for professors who have good performance in research.