Todd Holmes’s review published on Letterboxd :
One of those rare documentaries that is so essential as a journalistic document, the craft of the filmmaking is almost besides the point. It must be seen if for no other reason than to dramatically illustrate how important whistle blowers are in an age when governments and corporations have less and less actual oversight. Snowden has succeeded and essentially triumphed in this regard, especially considering revelations the film provides regarding his apparent relative domestic bliss in Russia. Meanwhile tragic figures like Bradley/Chelsea Manning suffer away in prison and have fallen almost entirely out of the public discourse--a flip side that is unfortunately not touched on at all in CITIZENFOUR.
Again it's hard to nitpick Poitras' decision to focus almost entirely on Snowden, and credit has to go to her and her editor Mathilde Bonnefoy for allowing his sequestration in the Hong Kong hotel room play out in such a long, quiet and studied manner. As cinema, CITIZENFOUR isn't on the level of something like Michael Moore's provocations, but as journalism it's as important as anything you'll see this year.