I'll hold off on comments on riding in a dress for a second, and simply say that on several occasions recently, I've ridden into and back out of town wearing a white shirt and a necktie. I make sure to carry my helmet in hand and comb my hair as soon as I'm parked and locked. It's more than a fashion statement, it's a (possibly not-so-) subtle message that "Hey, I did this, you can do it, too!"
As to riding in a dress, that truly *was* a fashion statement. I got people's attention, I stopped to talk, they could see that while my choice of fashion was loony, that I was a sensible person, out to make a point, and more importantly, have fun! Sure, I'd do it again!
btw, we need more women on bikes. In dresses. All the time, not just fun rides.