A lot of factors play into how bad 'Bras' are...
What color is your car? Color plays a big part in how fast it will fade and such! If you take care of your car and you don't put it on and keep it on 100% of the time than you should be ok! If you have a red or a Yellow on than I would be afraid to put one on... VERY VERY afraid
As Paul(87camaroPA) said, if you put it on for long trips than it is very purposeful. Not only will it stop stone chips, but it will keep those damn bugs off the car. You know what bugs I am talking about, the ones that take about an hour to scrape off since they are basically plastered on your front bumper/hood!
I would advice not to get a bra. Just some food for thought!