Karl Zinsmeister argues the war is over and we've won, which some are calling bold and perhaps premature, but I wonder if he actually understates the case. We defeated the main military opponent and won the real war in April 2003; everything since has really been mop-up/police work. The war itself was so easy in comparison to occupying the country and building a democratic Iraqi government from scratch that it seems as though we're still at war even though there really is little to no militarily significant opposition.
Now, had we bolted in 2004, we could have "lost" in the sense that new wannabe tyrants had a fair chance of overthrowing the interim gov't and re-imposing a Saddam-like tyranny. But now even that seems extremely unlikely, if not impossible, given their limited support from the populace. The Iraqi forces aren't quite up to defending the whole country at this point, but they're probably strong enough that if we left today they would hang on and eventually win (though it might not be pretty).
It's too easy to forget that
1) There are no standing armies opposing us
2) Elections have been held, creating a legitimate gov't
3) Polls tend to show the vast majority of the Iraqi population is firmly on the side of the democratically elected gov't
4) Iraqis are flocking to the democratic gov't forces in far greater numbers than to the insurgency
5) Unlike the insurgency, the elected Iraqi gov't has a continuing revenue stream of billions in oil revenue to bolster its position
6) A constitution enshrining basic freedoms and rights is 80% complete, with the constitutional referendum and later parliamentary elections now expected to be held on time
7) Iraq's economy grew at 50% last year, and growth for this year is estimated at 35%. This is very important, because as Fareed Zakaria noted in his book The Future of Freedom, there is a very strong correlation between GDP per capita and successful democracy; once democracies become rich, they become immortal. Between $6,000 and $9,000 GDP per capita (iirc) 2/3 of democratic states survive indefinitely. No democracy with a GDP per capita per capita over $9,000 has ever failed. Currently, Iraq is at about $3,500 GDP per capita right now, so in a few years they will probably reach the economic tipping point, esp if oil prices stay high and modern development of Iraqi oil fields happens as scheduled.
All that said, the violence will certainly continue for a year or two, and may continue for decades. But that shouldn’t be viewed as the final judgment on the war. Israel still sees violence 60 years after its inception, but they’ve managed to build a thriving society anyway.