From the Post:

The handover of the Green Zone from U.S. to Iraqi control Thursday presented such a powerful symbol of the waning American presence in Iraq that it would have been nearly impossible for both sides not to mark it with a formal ceremony.

They did, but the ceremony wasn't much. A podium was set up in the middle of a dirty street. Five small balloons and some tinsel decorated a seating area. The American ambassador and the top commander of U.S. troops didn't show up. Neither did Prime Minister Nouri al-Maliki.

Maliki instead attended an unannounced event where he watched what might have been one of the most stirring signs of the new Iraq: the raising of the Iraqi flag over what just a day earlier had been the U.S. Embassy. The decision to keep reporters away from this ceremony hinted at the unease and uncertainty both sides feel about the transition.

Almost goes without saying (but it shouldn't) that the transfer is largely a formality and U.S. troops are still providing security in and around the Green Zone.