Pros
Global reach. Mega brand which can get you a meeting with almost anyone. Chance to see/develop some cutting-edge new technologies if you are so lucky. As a foreigner at Korea HQ, you may be thrust into a role which gives you a chance to see the world through business trips. 3 free meals a day at the cafeteria and free shuttle bus transportation to/from work.
Cons
Initiatives and executives come and go at the blink of an eye. Poorly-defined roles & responsibilities for most employees -- this ambiguity causes a lot of project overlap among groups and you often find 2 groups working on the same project simultaneously, unbeknownst to each other. Excessive politicking. Little collaboration between groups. Still a very strong Korean hierarchy and junior level employees don't take personal initiative or accept accountability. Important meetings are held in Korean language and as a foreigner you get left out -- unless you have somehow mastered the language on your own time as Samsung does not provide Korean classes for its foreign employees (you do receive a budget for education but no clear way to use this effectively while working a full-time job). No flexibility at all to work outside the office, and your hours are tracked; i.e. you must sit at your desk for 9 hours/day even if you have nothing to do!