I've gone from saddlebag panniers and grocery baskets, to a couple of backpacks, a sling bag, and now a mess bag. The panniers and baskets didn't lend themselves to my multi-modal commute, so they sat around largely unused (plus I was having heel strike issues). The sling bag just doesn't have the volume that I require. My old Dakine 'pack wasn't waterproof or that comfy on the bike, so it was replaced with a Banjo Brothers (L) 'pack.

I grew tired of basically unloading the BB to find stuff at the bottom (lacks organization), and ended up trading my panniers to another BF member who wanted to get the weight off of his back for a BB mess bag.