I think people fail to realize that ending the AT&T exclusive _would_ make the overall iPhone experience better. Here is why.
Right now, everyone in the US (well, except for unlockers) is using AT&T. They are a clear bottle neck that can't handle the current load of iPhone users. Lets say T-Mobile were to get the iPhone. They couldn't handle it exclusively, they would crumble even faster then AT&T did. BUT, many people would leave AT&T to go for T-Mobile. Reducing the strain on the AT&T network and distributing the load across multiple carriers.
Each area has a different dominate carrier. In the Bay Area AT&T is presently doing awful. I am not totally sure who would be better, but with an option to switch I sure as hell would try to find a better carrier. If my next choice sucks, I will just switch again until I find a fit.
Will Verizon get the iPhone ? Sure, only a question of time. Will they get it before they switch their network to 4G ? Very doubtful. Adding CDMA into the iPhone isn't a quick and easy task. Its not a software update, it would REQUIRE a hardware change. Its something that is just not worth Apples time. Adding a separate network for a small handful of customers adds to development time and QA time. I say small handful because on the global scale Verizon is the only company they would offer a CDMA phone to. CDMA is on its way out the door. Regardless if it maybe or may not be better, the rest of the world is using GSM and Verizon is going to conform.