Another great article surfaced recently about AT&T and how it will be affected by Verizon getting the iPhone. The article is from PC World and it's called What does AT&T to when Verizon Starts Selling iPhones. It does a really good job highlighting the things that AT&T has done to deal with the network overload caused by iPhone users and at the same time preapre for Verizon getting the device as well.
People are going to switch, but AT&T's network has been built up to support the iPhone and, not mentioned much in many of the articles I've read, supports simultaneous voice and data. The Verizon iPhone, built on CDMA, is not going to be able to provide access to both voice and data. It's something AT&T's network supports but Verizon doesn't support until it gets to LTE. Why Apple would release a CDMA phone instead of LTE doesn't make sense to me considering people aren't going to be happy not browsing the web while talking on the phone.
When Apple comes out with a new version of the phone that runs LTE a few months later, Verizon customers will be dumping their CDMA phones and buying new LTE Phones. Good for Apple, Bad for Verizon customers.