First of all GIS series and movies must be watched in order to get the point.
Basically the plot in the GIS is: humans losing humanly features while machines gain those features. Simple as that the GIS is not just an anime its the critic of human society. So its also a deeply critical movie with political stubs added to the story line. So it can be rated 16+
To understand and digest the whole concept and philosophy in the series one must have a really open mind and little faith in religion etc.
The technologies introduced in GIS are not that authentic as many ideas have already been introduced to society long before (such as in Blade Runner and Space Odyssey), the strength of GIS comes from how it takes philosophical and social matters into hand.
Its an adult production not because of the bloody scenes or sexuality but from the depth of the subject.
Many people were bored of the long conversations, but GIS needed that to help the audience understand.
Anyway all in all GIS is a masterpiece and a rare delight. It reflects future logically and brilliantly without even needing to leave the planet and go as far as zillion light years away.
Of course it my opinion.

People are sleeping all the time;
at night on their beds;
at daytime on their boots...