A prolonged bout of road construction on my commute route led me to switch from panniers to backpack a couple of years ago -- things in the pannier were getting too beat up, and the pannier mounting hardware suffered repeated fatigue failures. It was pretty clear my commute cargo needed suspension, which meant either a backpack or switching to a full-suspension bike for commuting. With a backpack, the banana in my lunch bag doesn't turn to mush after riding brick streets and hopping curbs.