I finished it late Saturday/ early Sunday. If you go to BONUSES on the pause menu and then STATISTICS, you'll see your total time played stat. My first playthrough was 19 hours. That was so much more than a game. Definitely more than a movie. It was an experience.
The sounds were superb. Things like the sounds of your footsteps when you run from a Clicker... The sound of a dog barking in the background.. The birds chirping... These things are so subtle, but it totally added to the immersion factor.
With the foreknowledge that Grand Theft Auto V will be out later this year, I'm going to stick my neck out and say that this will be 2013's Game if the Year.... Or at least a strong contender.
I'm about 9 hours into a new Game Plus mode. I can't get enough if this!!