A 1.9L Z3 can outgun a Smart, and in the two seater world, that's about it. But, if you want a cool-looking cheap drop-top with the prop on the hood, it's the cheapest way to impress the curb-side mini-skirt set.
Be aware that it's still a BMW, and a not-cared-for example will run into the poor house with parts. A bargain is usually not.