A hot mess.

Rating: 5/10 (15 June 2015)

The good: Teller and Simmons commit like mad and sell the heck out of their characters -- basically, as many have pointed out, the only two real characters in the film -- enough to make their work together suspenseful and interesting to watch... no matter how silly the underlying premises.
The bad: Neither character is all that likable, but moreover the cartoon levels of abuse that "Fletcher" dishes out to his students and especially to the protagonist would get him arrested and drummed out of the Marine Corps, let alone a music school. In the course of the movie, Fletcher doesn't just play head games and dish out deeply personal verbal abuse which on its own should be enough to get him disciplined; he throws chairs, kicks stuff over, humiliates and *slaps* the protagonist, forces him (in hilariously over-the-top fashion) to play until his hands bleed in order to "earn" a part, and makes him take the stage at a competition having obviously just climbed out of a car wreck... then boots him from the band when he can't keep playing.
This character isn't an educator. He's an abuser. This is even made obvious by the suicide of one of his former students as a (minor) plot point. Fletcher is himself a (clearly mediocre) musician dealing with his own demons by desperately trying to become at least a footnote in jazz history, the man who threw a cymbal at the head of the next Charlie Parker. And yet...
The silly: ... we're treated to an end sequence where a "meeting of the minds" occurs that makes no sense for everyone involved and seems effectively to make excuses for and reward Fletcher's abuse. The disposable and irrelevant subplots meant to sell the rest of the people in the protagonist's life as representing mediocrity don't come off, either.