Let me set this straight for all in California. 70% is the only legal tint for front windows in California. For those not familiar with how dark that is, 70% is pretty much just a UV coat and does not give the appearance of a darkened window. The back ones can be as dark as you want, even painted black, provided you have a side mirror on both sides. My buddy has been tinting windows for well over 15 years and owns a tinting shop. Everytime I go to the shop he is putting tint on front windows but he has to tell them upfront that it is not legal. On past vehicles i've had my sides as dark as 5% and front windshield 20% but that doesn't usually last for more than 3-4 months if your lucky in a full custom frame draggin mini-truck. I got popped 4-5 different times with that truck. Now with my ST I just have the stock rear tint and 35% in the front and have yet to be hassled to the point I don't even try to roll the windows down when I see cops, but that's just really up to the whim of the cop. Just cuz you haven't gotten busted doesn't mean you can't or won't in the future.
If you are interested in other states here is a list of all the percentages
http://www.iwfa.com/iwfa/Law_Chart/State%20Law%20Chart.htm