The devil, as always, is in the details, and while I think that Gates and the DoD want to get out as quickly as is possible, Bush and His Evil Minions^™ really do want to settle their successor with Iraq as a firm commitment.

The sticking points:

But they have differed over some issues such as granting immunity to U.S. soldiers for acts committed in Iraq, whether Washington has the right to detain Iraqi prisoners and on the future command of military operations on the ground.

Same old, same old.