I honestly don't know what to make of Monster. A few things are easy to say: Charlize Theron is as good as everyone says, and it ain't about the makeup, she gets inside the character. Christina Ricci is also fine, although her character as written seems harder to understand. I'd also guess the movie is successful on its own terms. I don't actually know what those terms are, but I can guess that writer/director Patty Jenkins was aiming for a complete lack of glamour, and she succeeds.
The film is so good at anti-glamour that it made me question my fondness for other movies about society's dregs. Even a movie like Sid and Nancy, which is mostly non-judgmental, allows Gary Oldman to make Sid Vicious more likable than he probably was ... it gives us a way inside the movie. Monster doesn't do that ... this monster is never likable, and certainly never glamorous (this ain't Bonnie and Clyde), yet through the force of Theron's performance we feel like we've gotten to understand something of what made a woman into a monster.
The "facts" of Aileen Wuornos's life are grim; there's nothing to be done about that. But we can be thankful that Patty Jenkins made this film, and not Lars von Trier ... he would have invented a dozen other atrocities for Wuornos to experience, then lovingly degraded Theron until her performance disappeared under the crap he made her endure.
The only Oscar nomination here is for Theron, and that's appropriate ... I respected the rest of the movie without feeling any real connection to it, which may be the point. If I gave 1/2 points, this would be a good one for a rating of 6.5, a little under 6 for the movie but bumped up by Theron. I don't know ... it's not as good as Requiem for a Dream, which got an 8 from me ... it's about as good as Whale Rider, another decent-not-great movie with a rewarding lead performance. OK, I'm feeling generous: seven on a scale of ten.