Great thread, Saffer, I've wondered this a lot myself.
I have no personal experience living in any other Asian country, I've thought about teaching in Thailand or Taiwan or southwestern China for a year after Korea because I love warm weather and have perused a lot of Internet message boards from those countries. From what I gather, I'd agree with posters who say that the feelings are more low-key and criticism tends to center on specific things they'd like to see change or develop in the country, instead of a visceral dislike to the entire cultural structure. There's no message board out there that compares to Dave's Korea one, with its two opposing groups of people who either 1) See any criticism of Korea as bigoted, unfair, or ethnocentric and have long-winded, bizarre social theories they trot out to defend the country, and 2) people who find completely pointless, insignificant little details to be obviously signs of deep hatred and resentment towards all foreigners, everywhere, all the time, by all Koreans, and who believe there's absolutely nothing to be enjoyed about the country at all.
Another dimension here, I think, is that you tend to see these extremes more in Korea's longer-terms expats, as opposed to the 20something-I-came-after-the-recession crowd. Since Korea offers the best buck for your bang right now for people with just a B.A., I'm thinking it got the bulk of the economic migrants who headed to Asia in that 2009-2011 recession window. I'm squarely in that group and while you do get a few people with very strong feelings about Korea one way or another, most tend to have a more neutral take on things.