Does this different from state to state? How dark can you go on window tint these days?

It's location specific, I'd check with your local DMV or what ever it's called in CA, to be sure.

every state is different

I think for the most part you can't be any higher than 25% Also, I am pretty sure that mirror or limo tint is just plain out the door!

I think for the most part you can't be any higher than 25% Also, I am pretty sure that mirror or limo tint is just plain out the door!
In Texas you can limo on the back window.

I think for the most part you can't be any higher than 25% Also, I am pretty sure that mirror or limo tint is just plain out the door!
i got 20% on mine

I too have 20% on mine. The reason is that I have heard of the 25% thing and I wanted to stay under it in order to stay away from getting pulled over for too dark of tint! It has worked so far! (knock on wood!)