I live at the shore. Most of my commute is through shore towns and around the bays, which is a nice ride. The roads are quiet to one moderately busy road, but no highways. There are a couple of moderate inclines.
When I first started, I got two panniers for my bike, as I am an attorney and I carry files back and forth (I'm in the office everyday - no court anymore, so I dress really casually in the office). These panniers kind of just sat on top of the rack and had a small connection at the bottom. One day, I got to work and realized that one of them was missing. It had two or three files from work, my Ipod, my wallet in there. I was absolutely panicked. I called my husband, who came and picked me up and we retraced my route in the car. I found the pannier on the side of a railroad track that I cross. Everything was there. My husband said that I was lucky it didn't land on the tracks - NJ Transit probably would have called the bomb squad to detonate it, thinking it was a bomb left by a terrorist! I have since bungee corded the panniers and they aren't going anywhere now, no matter how big the bump!