I flew kilted on St. Patricks day from Albuquerque to Baltimore. The "x-ray" machine detected my 3 strap buckles and my metal hose flash clips. A cursory patdown was all that I got.
On the way back I went through a metal detector. It beeped, but since I had gotten the advice on a thread like this to put my strap buckles front and back, rather than on the sides, that is what I did for the second go through. It worked like a charm and I breezed through without any patdowns.
I must say, it certainly is very comfortable flying in a kilt.