I had to join just so i could post on this...tint on the front windshield is very dependent on tint in the rest of the car... for example, limo on the side windows with NO tint on the windshield is very dangerous. this is all optics. when you stare at a tv in a dark room, everything else is REALLY dark. Turn the tv off, and your eyes get used to it and you can see all around the room.
I have limo all around and 35% ont he windshield, and I have ridden around with people who dont even realize that the front is tinted (AT NIGHT)... now just the same with optics is this fact. Limo all the windows AND 35% the windshield, wait till your eyes get used to it, adn then roll a window down and you are sure to get a headache.
OH, and if you tint the front windshield and roll a window down so that natural light is setting the 'white point' and the front windshield is suddenly very dark. but it all depends on the brightness of the highest white point that is affecting your eyes..
hope this helps, if you do it, do it all the way. I drove a 300C with limo all around and nothing on the window, and it was impossible to take corners at night with fear of ruinning a set of 22" Dub Shaolins...