I actually like the ending, here's why...
The vast backlog of Hollywood conspiracy thrillers contains a multitude of films which follow the simple formula of small guy vs Big corporation in which the humble hero always wins, unveiling the truth and saving masses of people.
In this film, the ending was far more downbeat. From the moment a character comments that all major agencies (such as the CIA0 are funded by banks like the IBBC, it becomes a possibility hat Salinger really won't succeed.
What I really liked about the final scenes is the way that he failed to get a recording of the one piece of information that could have helped him take the bank to court. Then, realising this he follows Svarson, who points out accurately that even if he is killed, several more bankers will spring up to take his place. In the final scene, unlike so many Hollywood thrillers, the good guy is not triumphant, he's powerless, impotent. He shoots only because he has nothing else to do, knowing it will achieve nothing in the long run. everything he's been trying to do for the whole film (and in the years prior to it) has come to nothing.
So, while the film may not be perfect, I quite admired the pessimistic ending, along with many other parts of the film.