@m Simple solution to the bike theft paranoia issue: Get a beater bike and use it exclusively for short commutes. If riding such a beast offends your sensibility (I know, I'm an avid cyclist, too), don't even think of it as a bicycle. It's your "short commute zero emission vehicle." As for the calorie issue, I just factor my commutes into my workout time and figure I'd be working out anyway. Plus I'm probably saving a mint on future medical costs by staying in shape!