mr. snakedriver.......
this is a fairly new book, which is fascinating because it's got the NVA side of the story (somewhat).........anyway, in it, Col. Harrison (ret) interviews one of the former NVA commanders and asks him what the most feared weapon was in the US arsenal, and the guy doesn't hesitate and sez "the AH-1 Cobra, by far......" they were more scared of the cobra than B-52's............
(in fact according to Nolan in the book "into laos", the sapper attack on khe sahn during lam son 719 had the specific goal of destroying as many cobras as they could, as well as the Comand bunkers for the 4/77th and 2/17th cav because the cobras where wearing them out in laos)
see link to book...
http://www.ripcordassociation.com/hell_hill_top.htm