I don't have any personal knowledge of IST to add, but I do want to reinforce the idea that a rational examination of the statistical chances of being involved in a terrorist attack would nearly always lead to the conclusion that it's silly not to go. The odds in IST are presumably infinitessimal. But to me it's also often interesting (and reinforcing) to recollect that even when infinitesimal odds "paid off" (9/11 at the World Trade Center), even in the center of the bullseye of the most successful terrorist attack in (modern?) history, 70% of the people survived.

And I'd also like to reinforce the thought that to demur or delay any pleasure or opportunity for fear of terrorists is a win for them. For several years after 9/11, every time I'd safely get off an airplane, I'd imagine it as a small but in some ways very real "&+@% you!" to the terrorists. We're far enough away now from that time that I rarely have that thought upon disembarking any more, but I suppose that fact is an even bigger defeat for them.