On the cover of the September 15th edition of The Economist: Why they should stay. Excerpts:
"On the security front, the best bit of news General Petraeus had for Congress is that local sheikhs in some mainly Sunni provinces such as Anbar, west of Baghdad, have stopped fighting alongside al-Qaeda and are now co-operating with American forces. But these Sunni tribesmen are at best fair-weather friends who do not trust and are not trusted by the government in Baghdad. Their decision to co-operate with America for the time being has had little impact on the sectarian killing and cleansing in mixed areas. General Petraeus says that by embedding American troops in violent neighbourhoods his surge has reduced sectarian killing by more than 45% since December. But even if his numbers are right that is just a kink in a graph of killing that has risen for most of the past four years.
...If America could choose again, it would not step into a civil war in Mesopotamia. But there are worse reasons than preventing a bloodbath for a superpower to put its soldiers at risk. Having invaded Iraq in its own interest—to remove mass-killing weapons that turned out not to exist—America owes something to Iraq's people, a slim majority of whom want it to stay. It is hard to know how Iraq can be mended. At some point it may become clear the country has sunk so low it is simply beyond saving. But it is not possible to be sure of that yet."
PS: Also in this edition an article entitled Please go, some time. The author writes "The Sunni insurgents may be a bit less active because they are watching developments in Anbar province, to the west of Baghdad, where the Americans are helping Sunni tribes to set up paramilitary forces. The Americans want them to fight al-Qaeda there, but many Sunnis may be hoping to get American backing for their efforts to weaken Shia control of Iraq.
The Shias are less happy. Their militias now rival the Sunni insurgents as the American army's main adversary in Baghdad; the American deputy commander recently said that Shias caused 73% of all the capital's casualty-causing attacks in July. Some areas are riven by an increasingly bitter feud among Shias, between the Mahdi Army and its rival, the Badr Brigades of the Supreme Islamic Iraqi Council, a major party in the government."