Three schools:

3. Those who think it's neither a masterpiece nor trash, just mediocre.

I was fully invested in Phoenix's performance almost immediately. I felt sympathy for Arthur; I felt Phoenix did a good job of showing Arthur's anger and humiliation at not being able to control his nervous laughter condition.  Those moments were effective, I thought.

But after the subway killing, I felt the movie jumped the rail and only grew more and more preposterous as it went along -- and took Phoenix's performance with it. Even ignoring the lazy, cause-and-effect movie psychology (I'm an experienced social worker and dual diagnosis counselor, I know what real mental illness looks like), so much of what happens in the movie makes no sense. For instance, a single subway shooting involving a guy in clown make-up immediately inspires a violent and murderous city-wide revolt with people killing police in the street?

I've read some fans arguing that the movie is supposed to be preposterous, that the subway shooting was Arthur's breaking point that detached him from reality and that everything that happens after that point is all in his head. But that's a lame excuse, IMO, and is basically the same thing as the ol' "it was all a dream" twist.  And even if that is the case, the final scene blows that notion right out of the water.

Phoenix is a fantastic actor, but I think he's given better performances than this, in better films than this. For this movie to be given 11 nominations would make me believe that every other movie this year was so turd-tastic that this flick must have looked like pure gold in comparison. But I know that's not true, because I've seen better movies and better lead performances this year.  The only thing I would have nominated this flick for would be the cinematography. It really captures the gritty big city feel of the early '80s, while also making it feel modern.

Phoenix deserves an Oscar. And I'm sure some day he'll get it. But not for this performance, and not for this film.

My two cents.