"The tribal leaders (of the Anbar provence in Iraq) have slowly been won over by a combination of coalition perseverance and al Qaeda strategic ineptness.

In a counterinsurgency war, perserverance is the key.  We've been there long enough that we're now seeing the results.  From Strategy Page:

September 22, 2006: Coalition forces in Iraq have suddenly received the manpower equivalent of three light infantry divisions. They did not suffer any repercussions in domestic politics as a result, and now have a huge edge over al-Qaeda in al-Anbar province. How did this happen? Tribal leaders in the largely Sunni province on the Syrian border got together and signed an agreement to raise a tribal force of 30,000 fighters to take on foreign fighters and terrorists....

This is just one sign that the tide is turning in favor of the coalition in Iraq. Many of the Sunni leaders have decided that the Shia-dominated Iraqi government is not going away any time soon, nor is the democratic process. As such, the tribal leaders have now decided that it is better to be on their good side rather than to be seen as uncooperative. Constant Arab casualties in al Qaeda attacks – and al Qaeda's desire for a caliphate – have not helped matters any, either.

Winning against insurgents takes a long time.  It just isn't that hard to make a truck bomb or an IED, and it's just about impossible to prevent them unless you've won the hearts and minds of the population.  The Iraqis -- all of them, not just the Sunnis -- can be forgiven for being skeptical of the United States' sticktoitivity, but obviously we're convincing many of them.

Well done, lads, and hooah!