I'd obviously heard about the controversy surrounding this film, but had never seen it for myself until I found the uncut 2-DVD version on sale in France for just 3 euros a couple of weeks ago.
First, I have to concede that, as the great-grandfather of all found-footage movies, it obviously has a certain importance. Its influence on everything from 'The Blair Witch Project' to recent wannabees like 'Welcome to the Jungle' is obvious. The plot is reasonably intriguing and I found myself quite enjoying the opening 15 minutes. Then though, that first absolutely vile scene of animal torture (the protracted knifing of the coatimundi) made me feel physically sick. At least the other animal killings were pretty quick, although the kicking of the piglet was disgusting too. By then, I was losing any interest in the story, although I did notice that the human gore looks ridiculously fake - I've just rewatched one of the final scenes and it looks like the wig falls off the decapitated head. Also whilst using real natives may add an air of authenticity to the film, they don't 'die' very convincingly and when they are supposed to be chopping up the bodies, it is obvious that they are chopping the ground off to one side.
That's probably enough nit-picking. To summarise, Cannibal Holocaust has a certain value as one of the original found footage films, but it isn't particularly well made and the real animal cruelty is stomach-turning and clearly detracts from, rather than reinforces the director's message, which I assume to be "who are the real savages?".