I've got 27% (legal limit in SC) all around on my car and I love it. Matched with the dark interior, it gives illusion of a darker tint when viewed from the outside but when sitting in the car viewing out isn't a problem, even at night. I had 20% mirror tint on my S before and yeah it was a pain driving at night! IMO, the windows on the S are small anyways and don't require much tinting to keep the sun out. Going with 30 or 35% should suffice.

 

Some before, on the left, and after, on the right. The bottom two are both after and show how from the side, the tint isnt too bad, but from an angle its really dark. I'm surprised its as dark as it is. Good thing I didn't go to 20%, haha.

 

20% If I had to do it over I would go darker but thats me... only time you see it anyway is when it is raining....