It depends on the colour of the car.
I did a little research and the film I had decided was a titanium based film. The colour was gave it a polarised dark shade (black to midnight blue) and in the evening although a little darker, I could still see out.
It looked great on my black 307. The rear window tint allows 20% light in while the sides are 35% according to the Australian standards. I personally see no problems with the red shades or maybe silver. I cannot say much about the mustard or green coloured.
Have to agree with the other respondent and that is mirror tinting looks real tacky.
Kindest regards