The killing of insurgency leader Abu Musab al-Zarqawi is a major accomplishment for the Iraqi government and allied forces, without question. The question now is how much difference it will make in the hostilities there. Certainly the Sunni hatred of Shias, which Zarqawi worked hard to foment, will remain, as will the corresponding feeling of Shias toward Sunnis. That is the heart of the conflict, and this does not change that. Zarqawi was a skilled tactician and strong leader, but replacements will arise. However, it is important to remember that each leader killed is a message to the rest: We're coming for you, and it's only a matter of time. Leaders do make a difference.
Of course, having bin Laden's head on a platter would send a much stronger message, but let us be happy with each victory in the long process of bringing some sense to a highly disturbed region of the world.