I loved this film, it absolutely spoke to me in a way that few films I've seen do.
My biggest fear throughout was that at any moment the next scene would see Sam (sean Penn) and Rita the lawyer (Michelle Pfeiffer) deciding that the best solution to their problems would be if the both united in a marriage / pseudo-marriage, so they could lay happy families and all live happily ever after, blah balh blah ad nauseum. Thank God Nelson had more sense to drop a large hunk of semi-soft cheese into the middle of an outstanding masterpiece. Such a cliched and trite twist would have aboslutely ruined the film for me. Obviously, Nelson did not want to pedestrianise her masterpiece and so consciously steered away from such a soap-opera style conclusion.
Penn's performance is highly commendable - more Rainman than Forest Gump. Indeed, it represents what must surely be a turning point in his career direction. Full credit also to young Dakota Fanning (Lucy) who carried off a superb portrayal of her character and simply stole the movie!
I'll keep this short but suffice to say if you haven't seen this film you're missing something big. Not everyone will go to see this film but those who do will know that they have seen a truely magnificent piece of cinema.