I have never brought stemware to a restaurant.
I have eaten dinner with others who have, and I certainly appreciate drinking wine out of the nice stems rather than the clunky restaurant glasses. I understand why people bring their own stems, and I don't begrudge them that right.
That being said, I don't think I could ever bring stemware myself. There just seems to be something a little weird about it. I like to eat on fine bone china and with sterling silver utensils, should I bring them to a restaurant? Should I bring a dry-aged steak to Mortons and ask them to cook it instead of their wet-aged steak? I know that my point is a bit extreme, but for some reason I don't have a problem with bring a bottle of my own wine, but I do have a problem bringing stemware.
Maybe if I did, I would quickly get over my hang-up about it.