The assassination of R. Nixon

I don't know if this is the original title of the film, but this is the one with Sean Penn. This related the true story of a man who becomes crazy; and will try to commit a murder.
I went to see it last Friday, and I was really surprised by this film. When I went out, I had a strange feeling, a sad feeling for this man. You realise that there's something in him, something good and he just doesn't want to live in this society where you lye to sell a miserable desk!

If one of you have seen it, what did u think of it, how did u find S. Penn?