I've seen them worn at quite a few SCD events in Scotland and here, too.
(Admittedly, they are mostly just worn to rugby and football games.)

I think they can look great on the right person, but I prefer an actual traditional Jacobite period shirt.
My Dad has one and he looks great in his...






I wore one as part of a 'William Wallace' outfit for my last job. (I figured if they were going to make me be so Historically inaccurate I may as well go the whole hog with it.)
I have to admit, the outfit as a whole felt like it would be wonderfully comfortable to dance in!