Thanks for the great comments all!

Steve, no need for anything under the kilt except basic underwear just in case a fall were to occur...wouldn't want any untoward rashes in the wrong places. The kilt does occasionally fly up, but that heavy wool drops things back in place quite quickly.

Believe it or not, I am not the only kilted skier in the area. One guy, Bradley, makes it his mission to ski kilted so long as the BASE temperature (not the summit temperature) is 20 degrees F or higher (that's -7 celsius for all you crazy metric people out there).

The kilt, because of all the wool, ends up keeping my lower body warm, even when moving fast down the slope. My kneecaps get a little chilly, but as soon as I stop, they heat up again.