My windshield must be at least almost 30 years old and I think its the original one! I had several swirls and it had a white haze to it.
A buddy of mine used some Novus Plastic polish on it with a buffer and after one application, the difference was monumental! Its a 3 step process with the Novus chemicals, but Ive only used the number 2 polish and let me tell you, Im glad that I tried this before going out and purchasing a new shield.
My buddy took pictures, so I'll ask him to send them to me with before and after pics, wow what a huge difference!
http://www.novuspolish.com/