There are two responses to Citizenfour that I can foresee, depending on what you thought before you saw it. (Well, three. Indifference is a perfectly valid response, I guess.) If you go into Citizenfour with an extreme opinion either way about Edward Snowden, you’ll either leave convinced you were right to begin with, or your perspective will have shifted to the middle, because regardless which way you lean politically, Citizenfour paints a picture of Snowden that is decidedly anti-extremist. And if you go into Citizenfour without an opinion or just with little to no knowledge about Snowden, you’ll leave the movie convinced that the world you live in is entirely different from what you thought before, so convincing is the documentary’s atmosphere of modern paranoia. Regardless, this is one of the most important movies of the decade. As Drake/Future would say, what a time to be alive.
Quicker take: Reaction options to Citizenfour: I still love Snowden / I still hate Snowden / WHY IS MY PHONE MAKING THAT CLICKING SOUND