A friend of mine runs marathons; a 25k is a regular thing for her. When she was starting out however, she always ran with audio, mentally gauging mile markers by which part of a playlist she was listening to. It didn't occur to her that most official marathon's don't allow personal audio devices and she didn't learn this until the day of her first event. Though she finished, her time was completely shot and she didn't enjoy one leg of the race.
I committed to one year of health improvement sans personal audio so that my routine wouldn't be affected if I didn't have my ipod or if a battery died. Not that I was worried about a player making or breaking my workout but I wanted to learn my body and I didn't want any distractions. Now I enjoy music from time to time, when I need a bump or if I'm not feeling social at the gym.
Mix of Hard Rock when wanting a push.
Mix of Contemporary when wanting to zone.
A great benefit that I've recently taken up though is catching up on news, tech, learning and various brain stretching podcasts, especially during cardio. Exercise the body and the brain in the same time space = Double Rainbow!