Iraq is a big mousetrap / roach motel to get and kill various al-Qaeda and other jihadists who can't "lose" Iraq and thus have to divert and drain their human and financial resources and suffer very bad PR for massacring other Muslims and Arabs. We also get the only actionable intelligence from Iraq through DIA, via captured jihadists and disenchanted "insurgents" and formerly sympathetic populace which is now threatened by them, and need and want our protection... media "reports" notwithstanding.
We are also right next to the last Axis of Evil partner, and Iraq is also a "tripwire" which Ahmadinejad is trying to trip, and might just "succeed" - when we decide the time has come, there will be plenty of evidence of "acts of war" from Iran.
The strategy is very sound - we have a lot more problems in our "unCivil War" on home front, than we have in Iraq. Even State is mostly not freelancing and making the wrong noises at the wrong time - I assume, due to leadership of Condi.