I had my windshield tinted and love it. I don't need to wear sunglasses when driving anymore. The guy that tinted it does side jobs out of his garage and told me the same thing others have said, thats it not legal to do. He used a special film (maybe not special but a certain type)to do it and you have to be looking for it to notice it.

 

Here: http://www.tintcenter.com/laws/

Cali:
HOW DARK CAN WINDOW TINT BE IN CALIFORNIA?

Darkness of tint is measured by Visible Light Transmission percentage (VLT%). In California, this percentage refers to percentage of visible light allowed in through the combination of film and the window.
Windshield Non-reflective tint is allowed on the top 4 inches of the windshield. FrontSideWindows Must allow more than 70% of light in. BackSideWindows Any darkness can be used. RearWindow Any darkness can be used.

 

I got the front two matched up to the back...15% and then i got the solid back glass (which was already tinted) tinted with 15% as well and then tinted the windshield with 35% and a 5 % strip

 

in VA you can do up to 0 on rear windows as long as you have side view mirrors. on front windows the legal limit is 50% and no tint is allowed on windshields at all except the strip at the top. i got my truck done down to 35% but i had to pay cash and he didn't give me a receipt. he gave me a slip of paper with a code word written on it and said if there were any defects to show him that card and he would know he did the work and fix it. he's out of business last time i checked. it was a perfect tint job though.