I have Verizon, and so do others I have on my family plan, so I haven't seriously considered the iPhone.
The BlackBerry runs circles around the Windows driven Treo 700, but I wonder if the iPhone will really be a step forward or backward for my business application of syncing appointments, keeping track of emails, etc. I love anything Apple-related, but feel that the keyboard on the iPhone is difficult to use, because my fingers seem too fat? Seriously, how do you guys not mess up when aiming for the letters? I also find it easier to scroll using submenus, a wheel, and buttons, rather than pointing and pushing on a flat screen that requires me to use two hands.
No doubt the iPhone is the coolest new device in the industry, but not sure it would be practical for me.