I honestly don't know what percent my windows are tinted, but I've had them for almost 3 years and have never had any trouble (been pulled over once for speeding and nothing was said). However, my friend had a limo tint on his black Civic (no muffler or anything to make it stand out) and he was pulled over for nothing else other than his windows and had it removed. My girlfriend had a limo tint on her red Monte Carlo and she had to have it all removed besides the read window also pulled over for nothing other than windows.
My website in my sig has pics, but they're not the best to show the tint.