I started backpack and then went pannier. I prefer pannier just for the comfort level. Plus, I use a camel back for h20 and small stuff. Speed dropped a little on the "speed" sections but overall, it made no difference. Then again, because of stops and traffic I realized that there's not much point in busting my butt for speed anyway since it shaved maybe 5 min. off of the time yet kicked my trash for the day and the ride home. I even ditched the computer so now I have no idea how fast I'm going. I just enjoy the ride.