Extremely er "atmospheric" (i.e. SLOW) and somewhat amateurish but actually fairly effective, although not as effective as I'd like it to be. The violence isn't as shocking as it wants to be and my feelings towards the characters were definitely more apathetic than they should have been. Still, the faded brightly colored little houseboats and murky black water is forever tattooed in my mind, as is that final WTF image.
But then, I was also underwhelmed by "The Wailing" which seems to be highly regarded so I have a feeling that Korean horror just might not be my thing despite my love of "The Host" (which doesn't seem very typical of K-horror though I'm not familiar enough with the subgenre to be sure).
Never saw "Ichi" but I agree with your comments on "Audition". "Oldboy" is great IMO- own it and never get tired of rewatching it, can understand someone thinking that it sorta goes off the rails towards the end but "boring"? No way. Guess we shoulda known it was the troll all along.