I'm most impressed by how Satoshi's original vision has worked so well, close to its original form.

For instance, I think if Satoshi had not implemented block halvening, bitcoin could lead to environmental catastrophe, much like the thought experiment of a superpowerful AI being programmed to make as many paperclips as possible would destroy the world.  Block halvening kinda means that the world will never destroyed in order to create energy to mint money.

This is one of the many examples of immense foresight.