Pros:
– Tuition free monthly stipend (for undergraduates)
– Overall a good quality of education
– Good opportunities to do top notch research
– School is very well regarded in Korea (if you are planning to stay)
– Not a bad option to stay for undergraduate and then go to US/Europe to do Master’s or PhD, provided that you maintain a good GPA (which is hard here!) and have research experience
Cons:
– Social life is bad due to language barrier (Korean students do not speak English well)
– You can learn Korean, which will be a huge boost to your quality of life, but from my anecdotal experience people usually leave Korea after graduation, sooner or later, so Korean language skills become useless
– Food in KAIST is so-so, but there are many good cafes nearby including international cuisines (Korean food in general is very specific, so many people who are not used to this taste will not like it)
– Competition based education, students tend to not collaborate but compete with each other (this might be a pro actually depending on what you prefer)
– KAIST is not known outside of Korea