One of the things that most people comment on when reading on Midori is that it was actually banned originally for depicting graphic violence to animals. Now, what is on display here is rather shocking but certainly not enough to be considered obscene, especially considering the psychopathic nature of the character which performs the act. If anything, the act featured is only detrimental to children and as anyone with a brain has figured out, this isn't for children at all.
Personally, I was quite surprised by Midori. It was mostly animated and directed by the one man and it shows: mouths don't move often, backgrounds suddenly disappear, zooming in of a single picture is common etc. If anything, these shortcuts only add to the charm of the movie and how intricately personal it is to it's creator. There was apparently 5000 paintings handpainted by Hiroshi Harada to complete the film over a course of 5 years. It was also funded by Hiroshi's life savings; if that's not dedication to a piece of art then I don't know what is.
So the animation is charming, the characters are gut wrenching and the script is full of profound reflections. Another point is the music; most of the soundtrack is created by a keyboard and the dark melancholy keyboard noodlings really add to the circus freakshow setting in the movie.
This is a very dark and unsettling anime movie, so it's only best to watch this if you're looking for something that's profound and will make you think. It will hurt you emotionally and upset you but it will stick in your mind for days on end.