I didn't get any scratches, but I also had a full bonnet invisi-shield. The stripes looks exactly the same as the ones available from the factory. They were about $40.00. They stayed on the car when I was going over 100, so I don't see that as being a problem. The thing is to make sure your car and the stripes are clean before you put them on, and take them off frequently so dirt doesn't get between the stripes and the car, potentially scratching the paint. I plan on getting the magnetic stripes for my cabrio when it arrives next month.
Hope that helps.