Zombies see you from literally miles away and give chase. It's annoying because they are so far away they are literally a dot on your screen but they can see you even when prone and then they give chase. Because you can't do any skillful maneuvers around zombies if they all see you at any distance! Even at night time pitch black they can see you from that distance.
I hear that, officially, they can spot you from something like 1000 meters away, or something like that. God know's how. The world's best Snipers don't have spotting skills like that.
What I would like to see is a much much less vision distance but MUCH MORE zombies and also in hoards so you can actually sneak around plenty of zombies into towns rather than them all seeing you way before you have even entered the town..