I've been kilted on the trail for about four months now. I have a pair of Stillwater Thrifty Kilts, one in the "Irish National Tartan" (never mind that the Irish never actually had a tartan; mom's matrilineal line was of Irish extraction) and one (my anniversary gift this year; I think maybe Mrs. FLRider is trying to say something) in the "Black Watch" tartan. I like both, but the Black Watch is a lot less loud of a pattern (I wanted something a little more subdued but am not Scottish as far as I know, so the Black Watch was a good compromise).
I have to say, they definitely help with ventilation. I still wear compression shorts underwear underneath the kilt while hiking in order to avoid chafing, but the amount of airflow over a pair of regular running shorts is surprising. Also, due to the fact that they don't have to touch your body as much as shorts, they can be made of acrylic fabric. That dries much more quickly than any other piece of clothing I own, including my "quick dry" polyester athletic tees.
So far, I'm a fan.