I have 37% on the front windows of my SUV with 20% in the rear (rear is legal, front isn't). My wife has 37% all around her car. Enough to darken it up a bit and keep the harsh light out but not enough for the cops to care about us. Haven't been pulled over with it on for 7 years. If you're going for the dark look you'll want at least 20% though which will make you stand out.
My trooper buddy says he'll give a tint ticket instead of a speeding or moving violation if someone isn't being an !@#$, so it can actually help you save some cash in certain situations.
If you can't find a good place in Buffalo check out this guy in Rochester. High quality and by far the cheapest price I was able to find. May actually be worth the drive depending on the quotes you can get in Buffalo.
http://www.lindsaywindowtinting.com/