I have a black vinyl bra that I only use when the car is on track - the crap getting thrown up in that setting is amazing, and dangerous. I'll put it on for a long road trip as well, but take it off right away. Otherwise, the things are terrible if used in the rain and allowed to stay on as the car dries. The trapped moisture can quickly cloud the paint and, although usually only a temporary condition, it looks terrible. For regular use, however, it would be a royal pain in the butt.

Sadly, there was one day that I debated whether I should use it or not, and ultimately opted not to. It was extremely windy - 60mph gusts - and there's a lot of potential for blowing sand around here. There was one very short stretch of divided highway with maybe a 50 yard long stretch of sand in the median. As I approached it, coming out of a sweeping curve doing close to 80mph a huge gust blew fairly heavy debris right at the car. Trust me, with a closing speed of 140mph that crap did a serious number on the front of the car, with quite a bit of crap actually getting under the paint like a bunch of tiny slivers. While the bra would have prevented all that, it still wouldn't have prevented the windshield from getting sandblasted and a couple of small chips being taken out. Worst of all, the car had less than 2500 miles on it at the time.

Oh, and in my experience with clear bras, this problem would have done some noticeable damage to one of those as well. Of course, you can fairly easily pull a clear bra off and replace it, but still.