Ive got 15% on the back of my Lexus, a 5% up on the front windshield, and 5% at the driver and passenger windows, although im getting that changes so that its 15% all the way around.
PA really doesnt have a set law on the books regarding tint, at least not that ive read. I believe they go by, if thay can see through the window, your ok.
Just dont get pulled over. Secondarys suck :P
The problem with PA's Laws:
http://www.berksweb.com/users/dmv/tint/