I'll preface this by saying I've been been a Verizon customer for about 6 or 7 years (RAZR, Voyager, BB Tour), and before that I had a Nextel (i95 color or whatever). I have never ever had a problem with Verizon's service. Never a dropped or scrambled call, whether I'm deep inside the middle of the mall, or at work (inside of a hospital surrounded by thick walls).
I also have Wi-Fi at work, at school, and at home; so I'm covered by Wi-Fi about 95% of my day. My commute to all these places is the only time I will not be able to use Voice + Data simultaneously, and quite frankly, would you want to be driving next to someone using V&D simultaneously?
Now I'm not going to be like some of the pro-Verizon people on here and proclaim that Voice + Data capability is truly useless, and a wasted feature. I would love to have the ability, as I'm sure once in a blue moon, I could find myself in a situation where it might come in handy. Why would us Verizon customers turn down an added feature, unless you're required to give something up to get that feature?
That's exactly what would happen if I traded in my Verizon network in exchange for the AT&T iPhone. Everyone I know (in the metro-Detroit area) with AT&T has far inferior service to the people I know with Verizon. The doctors I work with and other co-workers that switched to AT&T solely for the iPhone don't regret doing so, as the iPhone was the only phone at the time that offered all those useful apps (and still in my opinion does it better than any other app-featuring phone), but now that Verizon is offering the iPhone, they are ALL switching for the superior service.
I've waited 4 years for the iPhone to come out. There's no way I would have left Verizon's network, because I loved the service; I had a feeling that the iPhone would come to Vz eventually; and because my iTouch worked just fine with my Wi-Fi connections.
Some of you AT&T customers experience great coverage in their areas, and good for you. Don't switch. Having people on multiple carriers is a good thing. I'm sure I wouldn't be as happy with Verizon if everyone rushed over to it. In a few years, when everyone is on LTE, maybe all this complaining and arguing will go away. Until then, just pick whichever phone, on whichever network, works best for your needs. I personally, couldn't be more thrilled that I can finally get an iPhone and stop carrying around 2 devices!