I just finished watching it. Had to separate it into a few parts, as I found it a little dull at times. This is probably not due to any shortcomings in the film, but because the general message of minimalism and frugality has always been second nature to me.
My parents were classic depression-era types and although the house I grew up in wasn't spartan by any means, money was valued, and purchases were thoughtfully made. On watching this film, my initial thoughts were that the message in the documentary was obvious. However, on seeing the various folk in the film who spoke of previous lives in which they had been addicted to consumerism, it struck me that this is an addiction that wasn't a widespread problem before our current consumer society really began flourishing. I'd argue that even nowadays, while some form of thoughtless consumerism probably affects many people, it only severely affects a certain proportion of the population. Some people abuse recreational drugs, others max out their credit cards, but both sets of people are attempting to seek happiness by "filling a hole".
To me, seeing all these folk talk about what a revelation minimalism was to them seemed a bit like watching someone talk about how their life is so much more meaningful since they gave up alcohol and found (i.e. became obsessed with) religion, for example. In the meantime, I'm watching it, and sitting perfectly happily with a glass of wine, while wondering what's wrong with moderate and thoughtful consumption. However, we do now live in a very different society from the ones that many of us grew up in, and I guess a lot of folk do lose their way. Anything that encourages people to use and enjoy their money wisely is a good thing, in my book.
Along similar lines, I do recommend watching the 2002 4 part documentary from the BBC, titled "The Century Of The Self". I didn't watch all 4 episodes, but did watch at least the first part, and possibly the second (it was a while ago). It details how Freud's theories of psychoanalysis have been used by the big ad agencies to sell things to people that they don't need, by using advertising to link mass-produced goods to their unconscious desires. Beginning at the start of the 20th century, when advertising tended to be much more straightforward and informational, the stark contrast with our modern consumer society that the ad agencies did much to help create (along with the marvel of modern mass-production) is very evident.