The above link is to an article in today's NY Times which gives a fairly balanced view of things in Iraq -- while things are demonstrably turning a corner, the relative peace there is not a certain thing for the days ahead.
The negotations going on right now at the highest levels of the U.S. and Iraqi governments are determining whether the current UN Security Council Resolution will be renewed (the one that authorizes foreign troop presence and gives them broad powers) or if it will take on a newer, more restricted form.
By entering Iraq uninvited in 2003, I believe the U.S. took on a moral obligation to help assist Iraq with what it needs in order to stand on its own feet as a democratic government. It's not our choice to either impose a Status of Forces Agreement (SOFA) the Iraqis don't want (well, we can't do that anyway, they're a sovereign nation) or to pull chalks and abandon them completely.
Unpopular SOFAs tend not to work so well (think about the way ours fanned anti-Shah sentiment in Iran in the 1970s), and neither does complete abandonment of allies (just think about the painful regret we're still feeling after disengaging from our Afghan allies in the late 1980s).