Important question is, how would've Iraq turned out without invasion in 10 years. I think the toppling of SH was a good move, just unfinished business from the GW1, but staying in there is waste of good money.
Let them kill eachothers as much as they like, as long as they dont distrupt much of our oilsupplies and dont acquire weapons that can bring devastation to the western nations (including Israel). If they wanna stay backwards, let them.