I have some pretty bad memories, and I have anxiety as a result of some of them, but I think (as Norad kinda eluded to) you learn from your mistakes, and you are a sum of your experiences. With that said, I've never had anything bad enough to cause PTSD (being a victim of a violent crime, for example) so I could see how it would be helpful for people incredibly traumatized by that.
What's confusing to me is this: "These early trials suggest that by messing around with the levels of cortisol in a person's body at the time of a stressful event, memories of that event might be impaired." So . . . . doesn't that imply that you would have to be on the drug already while experiencing the stressful/traumatic event for this to have any effect?