Following the Verizon iPhone announcement in January it looks like Apple and Verizon surveyed Apple Retail Store to determine which ones needed additional antennas installed to improve Verizon reception.
Not huge news considering big buildings like malls can play havoc with reception and extra antennas are typically used to provide better reception in many of them. It is nice to know Apple and Verizon are doing everything possible to make the launch go as smoothly as possible.
Just remember, it isn't the signal strength at a store you should be paying attention to, but the signal strength at home, at work, at school, and at any other location you frequent. If in doubt ask colleagues, friends, and anyone else using Verizon (or AT&T) in those areas what their reception is like.
Full letter after the break. Pre-orders start tomorrow!