I have some super dark tint on mine, I have it on the front and rear doors, also on the rear window.
If your worried about getting stopped, I would get a nice dark one on the rear door windows, slightly lighter on the front door windows, and get none on the rear window at all.
Sometimes cops will be at the end of there quota and stop you if you have rear window tint, not talking about rear doors, rear window, although this is perfectly legal in most states, in all states its illegal to tint your front windshield, so if your back one is tinted, they will stop you because they "have to check" you have not got your windshield tinted, hoping to find you have no insurance, no license, DUI or doing something illegal. I have mine tinted, I do nothing illegal, so I don't care, but if your worried, most tinting laws apply to the front of your car, but rear window tinting will give the law a reason to stop you.
Old Car: Chevy Cobalt 2006 LS Sedan base (Automatic)
New Car: Chevy Impala 2011 LT Fully Loaded (Automatic)