Panniers are great as the create a lower center of gravity and get the weight off of your back. I'm forced to use a messenger bag right now because my commuter doesn't have a rear rack option. Its fine in the winter, but definitely an annoyance in the summer. Its also annoying when I have a small number of items to bring, but still have the huge bag to lug around. If your pocket book and bike can accept panniers, then defintely go with them.