I've watched the whole documentary and these are my impressions divided into positive (+), neutral (±) and negative (-) remarks.
(+) To those who experience negative thoughts throughout every day this is a great opportunity to change their way of thinking. This documentary encourages people to change their lives in a positive way.
(+) The theory is explained in a way that's easy to comprehend. To those who are already familiar with this theory (resembling Rational Emotive Behavior Therapy) it may seem repetitive, but to newcomers this might be necessary.
(±) In my opinion, there are claims being made during the documentary that aren't backed up with solid proof. They do tell some remarkable stories, but it doesn't really convince me for some reason.
(±) Several times the interviewees give certain numbers and facts as proof of a statement they're making, but the methods of researching those facts aren't being explained. You just have to believe that what they say is true.
(-) At start The Secret gives the impression that you're going to watch a movie about a woman who will discover "The Secret", how and why it has been kept as a secret for so long, exposing a conspiracy and in the end revealing the secret to the viewer... But it's none of that. It's basically just a documentary.
(-) It's overdone. It feels like I'm watching Tel Sell, and the talking just goes on and on... (But again, to newcomers and people who need a periodical pep talk this might be just the right thing.)
(-) At a certain point, the documentary talks about a "constant state of joy" (at least twice)! The makers of this movie fail to mention that there is nothing wrong with grief and such feelings. If a family member or a good friend of yours dies, then why should you force yourself into a constant state of joy? It's alright to cry, be angry or whatever, as long as you don't exaggerate it, stay in control of yourself and act wisely. But the movie lacks in mentioning this.
(-) The documentary does seem to emphasize on money, welfare and "thus" happiness. I miss the element of growth. If you'd live life the way they recommend you to it feels so superficial to me... As if at the end of your life you only seemed to care about your own well-being.