I played for about 7-8 hours yesterday, which I haven't done with a game since "Arkham Asylum" came out. This game is great, and the world is so detailed. I actually find myself enjoying some of the quieter parts of the story because it gives me a chance to just look around and take in the scenery.
My one complaint so far has to do with the weapon selection. In most games I've played, when you run out of ammo in a gun, it automatically switches to the next available weapon in your arsenal. In this game, if you run out of ammo, you have to manually go in a switch to a different weapon. This pause has resulted in me dying more than once. It just really interrupts my flow, but it's a minor complaint, and it's certainly not ruining the game for me.
My roommate asked me what this game was like, and I told him it's like a mix of "Uncharted," "The Walking Dead," and "Children of Men." His response was, "That sounds awesome!"