Comments:

I use this bag on my S-style Brompton with no problems (no interference with steering or brake cables). It holds a lot and has convenient pockets on the back and sides. I use one of the back pockets for a compact U-lock. It's a good enough bag that I also use it as a travel carry-on; the frame can be removed, though I more often leave it in place to give the bag structure. I've noticed a little shimmying when I have the bag crammed full of heavy groceries, but it hasn't caused any problems. Only two minor quibbles: things stashed in the pocket on the front flap tend to fall out (they slide up to the top of the pocket when the flap is lifted and then stay there and fall out when the pocket is unzipped), so a more secure but still accessible pocket for small valuables would be great, and I'd love to see a key hook or leash.