I have all four side windows done at 30 percent and the rear windshield done at 20 percent. I went with these, because I wanted my car to look classy and not ghetto. I have had the tint for about 4 months with no hassels. Although, whenever I see a police car ahead of time, I make it a point to roll down the front windows just in case.
The officers in my area used to be a lot tougher on window tinting, but seem to have loosened up recently. I think a lot of it has to do with your attitude as well. If they see an average Joe looking person driving their four door, they probably will not do anything about it. On the other hand, if they see a slouched teenager with their hat on backwards and the bass booming, they just may use the windows as an excuse to whip out the ol' ticket book. Of course, if they cannot SEE you, they probably will just assume the worst.
My tip to readers without, but considering window tint: DO IT, but do it in moderation. 30% all-around will give you the coolness and visual appearance you are looking for.
Where to do it? I would recommend Fade To Black, it is a local entrepreneurship that will come to your home, resonable prices, lifetime warranty, AWESOME WORK, great guy. The number is 248-224-7624, ask for Jason Good. Tell him "Steve, the kid with the silver SVT and broken rear defroster lines sent you."