Oh, and with the Arkels. When you first get it it will seem hard to click on and off with the swivel aluminum thing. Just attach the 3 hooks to the rack, and to lock it on just pull the bottom of the bag out just a little bit to turn the swivel. Just a trick I found makes it a ton easier. I have the bug, the utility basket, and a whole set front and rear of the touring (large) panniers. I love all of them.

My friend is just starting commuting and I told him about the nashbar backpack pannier but I'll give him this link to let him think it over. Thanks for the info all.