TL;DR: If you like learning and want to understand the puzzles rather than just solve them so you can move on, than this is the game for you.

The Witness is a game that has many challenging obstacles to overcome, but it is also fair if you have done your homework. If you just rush through the early puzzles, it might bite you later in the ass. I see the game as metaphor for the process of learning.
And it is also an astonishing game set in a beautiful visual and acoustic environment in which you can stop and take a deep breath for a moment to relax your mind after a hard challenge. For me it is not something you want to rush, it is more a game you want to experience with a comfortable pace so you don't end in a state of tunnel vision. And if you sometimes look to your left and right you can discover something amazing that might get you to say “This game!” with a grin in your face.