My wife and I checked out Old Boy last night (she had seen it once before, but actually was really good about keeping quiet about the ending).
There's a really strong argument that Park Chan-Wook is the greatest living filmmaker. While I'm not really a fan of stylized violence, like Kinji Fukusaku before him, Park is one of those rare birds that when his defenders say that his violence is to end violence, it's actually believable.
I have sometimes heard the Tarantino comparison applied to Park. That's about as appropriate as comparing a six-year old at her first piano lesson to Beethoven--they both play piano, but that's where the resemblance ends.
Taratino's films are full of trendy eye-candy, but little substance. Generous on director's self-love and overindulgence, they sharply contrast to Park's deep overriding interest in the human spirit. While Taratino is fixated on the art of killing, Park explores the art of living.
While Oldboy rode its stylized action to prominence, it still possesses the brilliance of JSA, Park's best work to date.