They used to have a teriffic key lime pie here in Oklahoma at a place called Van's Charcoal Room. Alas, it's closed for business.
In my expierence with key lime pies, you gotta get the white/cream colored ones that are made with sweetened condensed milk and served on a homemade graham cracker crust. Some places have this green looking pie that is more like jello as many folks stated above. Stay away from the jello. Also many of the machine made crusts just don't crumble right. I think they are pressed too much and they loose their "crumbleablitly?"
As a general rule, when I travel florida I just ask the server if it's white or green. If it's green I don't even bother, if it's white well at least they are on the right track.
Any way, that's my 2 cents.