The remix of the main theme practically has a life of its own now.
Narm: The excessive cuts, overly dramatic music, and oddly music video feel of some scenes can make them a bit hard to take seriously. Going by comments from the director, this may have been intentional, though.
Christopher MacDonald as the "JUICE" infomercial/motivational speaker Tappy Tibbons, whose program Sara watches and she believes she's getting invited to as a "contestant". They filmed an entire presentation of the "JUICE" program in one day with MacDonald improvising most of it. At the end of the shoot, everyone in attendance gave him a standing ovation.
Little John, simply for being played by Keith David.
Dylan Baker as the doctor who turns Harry and Tyrone in. He squeezes quite a lot of performance into a minute or so of screentime.
Seinfeld Is Unfunny: The film's use of the "hip hop montage", a series of rapid cuts accompanied by sound effects, looks normal now, despite the fact that this was the film that popularised its use (Aronofsky previously used it in π.) This extends to the point where The Simpsons used a similar montage to show Homer's reaction to eating a McRib sandwich, which McDonald's themselves then copied for a bacon wrap ad.
Special Effect Failure: As sad as the film's ending is, it does get ruined when one notices Jared Leto's real arm pressed up against him can be seen under the blue sheet, and when people can see the cotton on the ground masquerading as snow (when the ladies try to console each other after seeing Sara) and that it was clearly shot in a summer day.
Squick: Harry's infected arm, which has practically withered away from repeated drug use.
Sara in particular comes off as the most sympathetic, having never gotten involved with the drug trade and simply wanting to have something to live for again. She plays the most part of a victim, being neglected by her son and doctor and appearing generally unhappy and lonely. Especially since she only wanted to lose weight and wasn't trying to get high in the first place. She is also a loving mother who genuinely cares greatly for her son, and this love seems to extend to Marion (whom she fantasizes about marrying her son, implying that she already thinks of Marion like a daughter and feels that Marion is a good match for him).
Tyrone, too, though he's not nearly as completely a victim of circumstance as Sara is. Of the four main characters, he's the only one who manages to get through the entire movie with his affection for his loved ones intact, and he's motivated primarily by his love for his mother... and then he ends up doing vomit-inducing hard labor as a young, black drug dealer in a Southern prison under openly racist guards. Some of the only touching moments in Winter are Tyrone holding Harry's hand in the work line, and calling for help because his friend is sick.