I have a messenger bag that clips onto the rack, and that's how I use it on my commuter bike. I've used backpacks but once I put things on the back of the bike it felt like I was freed from a burden. I also use the messenger bag over the shoulder when I take a Citibike, and that isn't bad either, but I keep the straps so it hangs low for when I'm walking with it, so it does get in the way a bit when riding like that. But this is for a Citibike and usually only a shorter ride.