I've had a clear bra on the front of my car for 2 years now. It has definitely prevented damage to my front end. I know this because there are spots that road debris hit the surface and damaged the film there. There's one spot where the rock was large enough to dent the fender and put a small rip in the clear bra. Fortunately, you can tell that the paint underneath is unaffected so if I ever remove the clear bra, I can go to a paintless dent repair shop and get it fixed.
I would definitely suggest that you get it professionally installed, and make sure that the pro has references. I had mine installed by a professional, and even he had a real tough time doing my front end. He won't touch another Honda S2000 after the problems he had installing mine.
The manufacturers claim that they last for about 8 years. If you check out various sports car forums, you'll find that lots of people use them and rave about the protection. It's an alternative to getting your front end repainted if you want it looking nice a few years later. If you ever want to remove it, you just put a heat gun to it and peel it off.