It costs more, but I'm a huge fan of this stuff:
3M Crystalline
Unlike many tints it is extremely clear (once the water is evaporated from between the glass and the film).
Living near Hotlanta, I have had to keep rags or gloves handy to be able to hold the steering wheel, but this stuff is great. For many cars (and especially hatchbacks) the windshield has the most surface area exposed to the sun, so on my VW, I had them apply the lightest colored film
to my windshield and the difference in how hot the interior get is amazing. If I am wearing dark pants and the sun is full on, this film makes a huge difference.
Sure, it is illegal to add tint to the windshield, but it is not like the police are looking for it, and this stuff is too light in color to draw attention.
I completely forget it is there except when I realize I am comfortable in a situation I expect to be too hot!
The only down side is you would lose the film if your windshield was replaced (be quick to use window repair services before the crack lengthens). Also, I do not mount my GPS on the windshield because I am worried that the film might abrade where the suction cup contacts it, leaving a hazy ring.