The biggest problem with darklight (in terms of aesthetics) is the fact that the head doesn't turn. As a result, when you are fighting, your character is always looking away from the enemy, when you're riding on some mounts, your character is looking straight at the ground. It breaks immersion.
In terms of practicalities, when you upgrade from DL you are forced to downgrade half of it. While other people may upgrade from iLv70 head+iLV70 chest to iLv90 head+iLv70 chest, you have to upgrade from iLv70 head+cheat to iLv90 head+iLv60 chest.
So the two problem (one aesthetic one practical) combine to make the darklight hoods/tin cans the target for player hate.