Well, it's a genre film. It is a classic film noir with all of the characteristic elements, you could check them off- chiaroscuro lightning, alienated protaganist, fatalism leavened with saucy banter, moral ambiguity, etc etc etc. It may die at the box office but will have a long afterlife in film studies classes.
I love this time of year in Seattle for movies. It's as if the dregs of all the summer schlock have finally been washed away by the incessant rain, giving us more than a few good reasons to while away the dark hours in a theater...
Mike Peska's interview of the director for The Gist noted that Gyllenhaal lost 28 pounds for this role and his eyes look huge because he was too hungry to blink.