It's funny (to me), but reading the Globe and Mail article referred to by Jim's post, made me assume that Chipman's comments were overwhelmingly negative. For example, the Globe and Mail uses adjectives like "dire" and says that the occupation and invasion of Iraq "proved" to be "powerful recruiting" points.
I then went and read Chipman's press release and it reads (to me) completely differently. To be sure, Chipman lists many criticisms (and I don't disagree with them), but it's much more balanced, with some room left for optimism, and little "proven" or "dire".
I've never argued that the Iraq war didn't have the potential to increase terrorism in the short term. I don't think even Bush claimed that there would be no short term increase. The long term is more important.
Even more important to me than the amount of terrorism in the long term, is the likelihood of the terrorist acts causing the downfall of western (and maybe all) civilization. The West can probably withstand suicide bombers and snipers and the like. After all, Israel does it, and we can probably get used to it too. And I think we'll have to. We can most probably even withstand a 9/11 size attack every few years and I think we'll have to learn to deal with that as well. I think we can most likely recover from chemical and biological attacks as well.
But what we may not be able to withstand is a nuclear attack. If terrorists manage to set an atomic bomb off some major U.S. city, that may well start a rapid progression towards the end of civilization. And then billions die.
I think it is unlikely that the terrorists can put together a nuclear weapon on their own. They will need a state sponsor for that. I think that Iraq was a potential state sponsor. Maybe not, but to me it's not worth taking the chance. I'm certainly willing to put up with more small scale attacks to potentially avoid the big one.
So yes, I feel safer.