1. It is a recently developed area (the last 20-25 years) , and hence it is not bogged down by narrow roads or old architecture. Much of the area is modern and well planned.
2. It is a misconception that only millionaires live here, it hosts even the moderately affluent who are willing to shell out a lot of money to stay in small apartments.
3. An address in Gangnam is prestigious, but the house might not be big. People spend more per square metre (In fact double around 10,000 USD per square metre), and in most cases manage with smaller apartments.
4. Branded stuff all the way. Apgujeong, Rodeo street, COEX mall:they all sport the Pradas and Guccis. Seoul itself is obsessed with big brands, it is not uncommon to see a line of customers waiting outside Gucci stores to gain entrance.
5. Gangnam's schools are supposed to be great, so families prefer to put their kids in school here, and it is possible only if their residence is in Gangnam, Apparently of all districts in Seoul, Gangnam has the maximum number of students who get into the prestigious Seoul National University.
6. Transportation is cheap uniformly in Seoul, however Gangnam by virtue of its location on the southern fringe of Seoul, lets you live in a hi tech city Seoul and commute easily to Suwon ( a smaller city 80 kms away where Samsung and other big companies are situated)
7. Gangnam has an International feel to it, foreigners find it relatively more comfortable to hang out here.
8. Upscale Entertainment options are plenty! It is plenty in a lot of areas of Seoul, but its more prominently visible in Gangnam.