In reality, the 90% tint really doesn't look like the car is tinted at all. I chose that for several reasons...this 3M material rejects as much UV and IR as most other films that are MUCH darker, has no metal in it so it does not affect radio or gps or cellphone reception, and doesn't draw attention to the car from police. Now, if you really want darker, they do make it in as dark as 35% (I think), which is very hard to see through from the outside. If you're looking for privacy, a dark tint could be useful, but is illegal in most places on the front windows...having the same one on all with this stuff works just fine, for me. Now, if I lived in the desert, just for the glare, I may want it darker, but where I live, I think this will be fine.
I have had it on my GT for about 2-years now, and the interior temperature difference is very significant. This 3M sheeting is the only one recognized by the American Cancer Society as a reliable UV barrier and is used on many police, ambulance, and other official vehicles.