I have always notice this about Verizon. Verizon typically performs horrible in-doors compares to ATT. And yes I know this depends on your location and all that. But I have been to several different states and always have a friends with ATT as reference. As soon as I go into a super marker or a mall the signal would drop to one bar and 3G becomes useless. Now that I have the iPhone 5 I have observe the same behaviors.
I have also noticed that the 3G and LTE on the iPhone 5 is very inconsistent on Verizon. Since I drive to work and I usually have to wait at this long red light every morning at the same location. Over the last several days, I noticed sometimes I would have 3G and sometimes I would have LTE. Not sure about this inconsistency.
Also, my room is in the basement (with a huge window), and I just have to say Verizon SUCKS, I can't have a complete phone conversation without somebody doing "hello, I can't hear you hello...?" Every single time, and my friend's ATT and T-mobile are working just fine.
I still have the Verizon unlimited data plan with me, but in a year or two as soon as Verizon tries to edge us out. I'm going to try ATT for sure.