Yeah, you can get a medical reason to make it legal. Otherwise this goes state by state, and is usually not legal for full windshield. Basically while you might think you can accept the risk, you're also making a risk decision for the other people around you whom you may also be impacting.
It does look
really nice but definitely never, ever utter a single word of anger if you get pulled over for it. You've made the choice.
You'll probably also have to sign a waiver of responsibility to the installer, depending on how many times he's been harassed by kids who didn't know the laws.
By the by, a quick Google search can reveal a site that lists all the tint laws by state. I'd link it, but being an IT security guy, I'd prefer not to send people off to sites I can't say you should trust or not.