I've got the REI novara panniers. probably not the best but with $40 I spent and the REI guarantee I am satisfied. I'm on my second pair. I do tend to try and mash everything in there so that probably puts more wear and tear on them. You can put paper bags in there and have some room on the side for my lock or something else (cereal anyone?)

as a bonus, I'm not worried about leaving them on the bike: not too expensive and not a lot of bling factor. I do get an occasional "goodie" from time to time.