I'll confirm that attitude goes a long way with a cop. He's thinking, "Is this guy going to shoot me?" Once he realizes that you don't pose a threat, he will be generally more reasonable if it is in him.
Also, unless you live in or are going through a small town where the cops don't have anything better to do, or you are doing something to garner police attention, you'll probably not have too much problem with tint. Heck, in Philly, you can drive around with no tags and spewing smoke as you blow red lights and you probably won't get pulled over.
