I don't like wearing a backpack mainly because my hair is long and the backpack tugs on my hair all the time. I do like the convience of a backpack to take the more important stuff with me when I lock my bike. So whai I did is to put a backpack inside my pannier bag and load my stuff in the backpack. This allows me to take the backpack with me and leave my pannier behind when I leave my bike after locking it.