With the departure of the 4th Stryker Brigade Combat Team, 2nd Infantry Division across the Kuwaiti border (the CENTCOM photo at right shows them leaving Baghdad), the US combat mission in Iraq is officially over, though no one is raising "Mission Accomplished" banners this time. With 50,000 troops still in-country on advisory and training missions, and the Air Force flying cover, US troops are by no means out of harm's way, and some may be tempted to call the whole thing a bit of a sham to comply with a campaign promise.
But it's more than that. I think Juan Cole gets it right in his post on the subject: the importance is to show the Arab world that our intentions are not to stay in Iraq, and that we really do intend to leave. (I may not agree with all the other points in Juan's post, but I agree on that one.) Our effort in Iraq is aimed at ending our mission, not extending it.