I'm one of the few people that like to soak up every bit of the game. In the first level, I explored a little and saw one of those 5 story high spiders walking around. I talked to people just to watch their faces. The list goes on and on.
I like to do that too. My first time I was able to get in, I kept throwing stuff at that (mild spoiler) one guard who makes you pick up the can and pretending he was Gabe Newell.
The game reminded me of Unreal the first time you step off the ship, the first time I was out in the square.