All depends where you live, Some state's it's illegal..
Bonus of Tint:
Cooler an Faster A/C temps
Saves your Interior Color from fading
If dark enough, more privacy
On a Buick GN it Looks Bad Arse!! instead of looking like a fish bowl in Black frame
Cons of Tinting,
If have Rear Defrost,Impossible to replace after long period time
If have pour vision ,night driving can be difficult
If go too dark you'll get pulled over a lot
Be sure you go to a place that offers a lifetime warranty,an plans on staying in business that lifetime!!!
I went 5% on rear an probly go just a little lighter on sides to please State Troopers,I opted for a strip on front windshield too..
Enjoy!