This is actually one of my favorite features of the game. I think it's good that they give NPCs personalities, it's makes players less willing to go on a rampage through the level or kill unnecessarily. It makes them more than Goombas that have to be stomped to advance through the level. Plus, one of my hobbies in stealth games is to listen in on guards talking.
Less than three weeks to go now. And until then, we've got the Sniper Challenge. Still.