Not surprisingly, it's a brilliant piece of work. On the level of Twin Peaks or The Decalogue or The Singing Detective in terms of made for TV greatness.
Even the opening is astounding and bears multiple viewings.
The animation itself is simple. It's use and reuse, that's another thing.
I love, in particular, the double exposure of the animation over itself during the character zoom.
The series doesn't have the emotional kick of Paprika or Tokyo Godfathers, the storytelling and intellectual arc may exceed everything else in Satoshi Kon's too small body of work.