I had a friend ask me about LTE coverage today because he saw that I was pretty enthused about having it on my iPhone. He asked if I was getting better coverage with the new phone on LTE than I was getting over AT&T 3G previously.
Here's the thing- Neither the AT&T nor Verizon version of the iPhone 5 uses the LTE network for voice calling. It is for Data only. Though they have both indicated that it is coming in the future, Neither carrier offers it yet.
What this means is that the voice coverage is identical to what you have on a pre-LTE iPhone.