My commute is over 15 miles one-way. It's too long to sit upright and catch wind, or get low and hurt my wrists on flat bars. I've ridden it with flat bars and the only thing better was how slow and in control it felt to go downhill in a narrow bike lane because I was so unaerodynamic. But since I've commuted on that route hundreds of times, that's not really a trade off that's worth making.