Does using a screen protector affect reading ability on kindle 3?

I have been using my kindle 3 for about 4 months now and noticed that there are a few scratches on the screen which is because of casual use. I am wondering if applying a matte screen protector on the kindle 3 will affect its quality considerably? I know adding a layer will equal to glare but will adding cancel out the excellent e-ink technology? Help please! And could anyone suggest something I could get?