Love them, I have one of them on the drive side of my Commuter / Grocery Getter (old Schwinn World Tourist) with a Wald 137 basket on the front. The 582 folds up out of the way, but take a minute to really look at how it folds, get it right and you can fold it back up nice and neat. If you just flip it up without looking it will not clip closed. I have seen a few where they gave up and just left it unfolded or tied up with string!
I think it works great, it is just the right size for a standard grocery bag (rectangular paper). I leave the non-drive side of the rack open for other bags I can clip-on.
Take your time mounting it to make sure it is secure, you do not want it to rattle when empty and it needs to be solid if you put 20lbs of groceries in it.