How's Won Bin's acting this time ?
Is he as good as before or better ?
This hard-to-get actor appeared in so few movies !!
Here are some critics comments that may answer your question. IMHO, his performance is as good as before, or even better because this character is difficult to portray and he did a good job. I also love his acting in Taegukgi and My Brother.^^
Won Bin exudes guileless charm as the dim-witted son, and is almost unrecognizable from his usual heartthrob image.
http://www.hollywoodreporter.com/hr/film-reviews/film-review-mother-10 03973839.story
Won, who began his career as a boyish-looking teen idol, is almost unrecognizable here as the complexly layered Do-jun
http://www.variety.com/index.asp?layout=festivals&jump=review&; reviewid=VE1117940276&cs
She plays the over-bearing mother of a not-quite able son, Do-joon -- played competently by a homely looking Won Bin -- who is charged with the murder of a high school girl in an unidentified rural town.
http://www.koreaherald.co.kr/NEWKHSITE/data/html_dir/2009/05/23/200905 230019.asp
But Kim could not carry the film without Won, who convinces the viewer to sympathize with his single-minded Do-joon, always distracted though he has flashes of lucidity.
http://joongangdaily.joins.com/article/view.asp?aid=2905707
Won Bin brings both tenderness and an unexpected level of chilling seriousness to his role.
http://english.ohmynews.com/ArticleView/article_view.asp?menu=A11100&a mp;a mp;a mp;a mp;a mp;a mp;a mp;no=385414&rel_no=1&back_url
Although I never really paid attention to Won Bin's previous drama and film work mostly as a "pretty-boy," Do-joon's revelations and moments of "clarity" is where he shines, with an uncanny knack for gripping urgency that shakes up our expectations of this helpless character.
http://www.koreasociety.org/film_blog/reviews/mother_by_bong_joon-ho.h tml
The son is also very good and at times and I've been told that he (Won Bin) is well-known for being able to pull off any role.
http://sheetalmakhan.blogspot.com/2009/06/korean-movie-mother.html