I've watched this documentary several times over the past few years, which is a testament to it's quality. Miller's respect for both the subject and the intelligence of his audience creates a refreshing documentary.
A rough history of disbelief does not use visual gimmickry to keep your attention, instead the series tells the story of the history of atheism from the time of the Greeks to the present today and explains concepts of theism (belief in a god/s), atheism and anti-theism (objection to theism) in a thorough way through the writings of historical figures and the evolution of ideas.
Whether you are a theist, atheist or apatheist, I strongly recommend this documentary as a way of accurately understanding what atheism is, what has caused it, attitudes towards it and how it has manifested over time.