I bought this basket for a mountain bike, though it seems to be aimed at the okusan (housewife) frame. It folds flat (the front folds in, then the sides, then the base comes up parallel to the rear face) and is spring loaded to open.
The basket itself is a little small, though it readily accomodates a large "my bag" shopping bag for groceries. It is also strong, and capable of supporting significant weight (several large PET bottles, for instance). If the rear face is well supported by the including bracket, there is no need to worry about the basket bending down (the sides and front hook into each other when open).
I did find that on a mountain bike the included bracket did not position the basket well, because the handlebars sit further out and the two hooks are bent backwards a little (pushing the basket out further). When heavily laden the base would rub against my front tyre. I fixed this by buying some long bolts, and a few washers/nuts from D2 to hold it out further from the frame. The basket now sits with the rear face parallel to the forward shaft, and the base never hangs low enough to rub against the front tyre, even fully laden.
If you are hoping to travel with a folding bike this is an excellent choice. It is easy to remove (a Leatherman or other pocket pliers/wrench would be handy if you adopt my solution above) and packs flat, a huge advantage over normal baskets. It's also easy to take off and stow away in the garage or somewhere if you're worried that a basket emasculates your otherwise very manly mountain bike.