Many reviews here focus on whether you can suspend disbelief on Sean Penn's performance as a retarded/autistic man. Before going into that, I'll go out on a limb here and say that the mental defects were incidental to the plot, the real issue was how much love Sam (Penn's characte) has for his daughter, Lucy (played by Dakota Fanning). These performances are masterful, Penn really departs from his trouble maker persona in so many of his earlier movies and shows depth that I really didn't expect from him. This is a breakthrough movie for him, and shows a range far exceeding my expectations Dakota Fanning gives a remarkable performance (I want to see her in other roles). I'm not very familiar with the behaviors of mildly autistic/retarded people, but I did find the Sam character believable. I think part of the issue is the same phenomena as Forrest Gump, that is the genius of the actor comes through, so you have a "brilliant idiot" As the father of a young daughter, I could relate. Michelle Pfeiffer's character was O.K. but not really central to the plot (her acting was O.K. I guess, but not great). My wife found the intrusive nature of the way the social workers were portrayed compelling. Other review have compared this movie to Rain Man and Kramer vs. Kramer. I thought this movie was more powerful than Rain Man (which was also good) but I have not seek Kramer vs. Kramer so I cannot make that comparison.<br /><br />I gave the story a 9/10, but if your not a parent or don't like emotional movies you might give it a lower rating.