There are two big ideas in the Iraq Study Group's report. The first is that a "cut and run" strategy would be a very bad thing to the region. This is unappetizing to the anti-war left.
The other idea should be just as unappetizing to the right. This is the suggestion that the US start open negotiations with Iran and Syria. This is a return to the realpolitiks that caused the US to support Saddam against Iran in the 1980s.
First a bit of background. As much as I hate to say it, Iraq is looking more like Viet Nam. Viet Nam was a proxy war between the US and the USSR. Our "peace agreement" in 1973 called for the USSR to slow down support for North Viet Nam. This allowed us to leave behind a stable South Viet Nam (until a couple of years later when we cut off support and the USSR ramped up their support).
Iraq has become a proxy war with Iran and, to some extent, Syria. US troops have recently found insurgents armed with weapons recently manufactured in Iran. Both Iran and Syria are hoping that they can induce enough suffering to get the US to leave and to break up Iraq into chunks that they can swallow.
The ISG report is essentially suggesting the same exit strategy that we used in Viet Nam. We talk Iran and Syria into slowing support for the insurgents long enough for us to stabilize the country and get out. What happens after that is no longer our concern.
That is bad enough in itself but there is the question of what we will have to give up in order to get these concessions. The most likely concessions are the Iran will continue its nuclear program and Syria will retake Lebanon (assuming that Hezbollah hasn't taken over Lebanon before we can start negotiating).
The long term consequences of this strategy are enormous. An expanded, nuclear Iran is a danger to the world in general and the US and Israel in particular. The loss of Lebanon will likely draw us into future conflicts involving Israel, alienating us further from the world's Muslim population.
The worst result is that this will cement the world's perception that the US has no stomach for a protracted war. Everyone involved remembers Viet Nam and our bug-outs in Lebanon and Somalia. For decades to come, any force we fight will know that all they have to do is keep fighting long enough and we will leave.