Window tint- pros cons and any good philly area shops?

My demon was originally a 340 car, but that's long gone, and with the soft market I'm not as into caring about resale value as I used to be. I decided to refresh the satin black paint and I'm thinking about tinting the windows (all but the windshield). This is partly for looks and partly practical. I almost always drive with both windows open, and I can't see much out the fastback window anyway with SS springs giving me a little rake. I'm hoping to make my all new stock (legendary covers, new carpet) interior last a while since I drive a lot and park in the sun fairly often.

What percent tint looks good and you can still see OK? I like the factory tint in my 04 durango back windows. What should I look for in a shop or expect to pay? Why might this be a bad idea?

Thanks!

I don't know if you've done this or not yet, but you might want to check out your state inspection laws concerning window tint. The last thing you want is to spend that money putting all that nice, purty tint on, only to have your local law enforcement make you pull it all off on the spot while they calmly watch (lol). DAMHIK.