I think a $10 pair of sunglasses ($150 prescription glasses in my case) is way cheaper then tinting the windshield or side windows.
On the 10 o'clock news (Chicago)a couple nights ago ran a segment on tinted windows. It seams that Chicago cops are ticketing cars with heavy tint on the front side windows (windshields will get you shot--just kidding), even though the state says they are OK. Chicago says home rule allows them to override the state laws. And with the city being almost bankrupt...that's another money maker.
If I was a cop, I don't think I'd want tinted windows anywhere on a car.
I lived in Temple, Tx. for 5 years, never had a problem with the heat in my cars. I either kept the windows open a crack or just turned on the air a couple minutes early. I also used one of those windshield sunscreens and still do to this day here in Chicago during the summer....they make a HUGE difference.