It seems the crossbow's usefulness depends on how you play. I like to play without running guns blazing into a town, so I rarely ever have to worry about attracting a horde of zombies. And now if I do catch a zombie's attention I like to take it out without bringing the rest of the townsfolk, or any nearby bandits on me. As such the crossbow is suited perfectly for my needs.
Yes the crossbow is pretty ineffective at a long range, but if you're at such a long range then what are you doing trying to shoot them anyways? You don't need to worry about a zombie unless they are nearby. In fact, most all zombies you encounter you don't have to worry about at all, because you can sneak around or outrun all of them. (provided you didn't already break your legs doing whatever it is you're doing)
But anyway like I said, a weapon's usefulness depends on the playstyle, which pretty much goes for every item in the game.