I really like the Deuter bag. In fact I own a Deuter BP and panniers. When in the drops I agree with those that posted to go with panniers, if affordable. When riding upright(mnt or hybrid) a BP is fine, in fact preferable(IMHO). Often heel strike is an issue with rear panniers on a mnt or hybrid. Here's a link for Deuter
http://www.deuterusa.com/
Charlie