With all due respect to the person who wrote the first review saying the footage was 'second rate', I think he misses the point. The reason why a lot of the clips aren't well shot or famous is because they are shot by amateurs about amateurs - this is a film about real life, and about a common humanity. Incidentally, there are shots of astronauts and atom bombs, and also some very famous clips, such as the clip from the old film 'the kiss' and the infamous shooting of a Vietnamese man.
The giving birth part of the film was for me rather painful to watch, which surprised me because, having seen Irreversible the week before, I didn't think anything could shock me. Many of the clips were funny, and others moving, but the film was flawed for a number of reasons. Primarily, I was confused by the order in which he tackled the various themes, which instead of going chronologically from birth to death exploring themes in-between, went from birth to death to rebirth, religion, marriage etc.. Also, having spent about 20mins on childhood and the teenage years, he spent no time on the elderly, unless you count the 'death' part.
I also felt that the plinky-plonky music didn't really help much, particularly during the 'sex' sequence. Why is there freaky jazz music going on over the sex part? Why is sex portrayed as some strange, subversive, aggressive part of life? I'll never understand why in 'serious' films hardcore sex attracts aggressive jazz music, when if you watch a hardcore porn movie it always has soft jazz music.
Although there were many parts of the film I enjoyed, it didn't have the coherence or forward thinking approach of similar films such as Koyaanisqatsi.
P.S I don't know why people would walk out of a film like this - it was marked '18' in the UK, so some of the scenes were expected, and all the reviews I read for it clearly stated that it was a series of clips put to music. Besides, it's not that long.