i routinely comfort myself at the thought of my u-lock's accessibility should i need it in a fight, and i've learned how to hold it to inflict maximum damage while protecting me the most. but at 5'6" and 125 lbs, i usually choose the 'bike like hell' route.
i had a friend put out somebody's window with his u-lock, and although it sounded pretty tuff, i wondered how that drived would treat the next bicyclist he encountered.