Only your mileage may vary
AT&T is evil, let's get that out of the way, so if the iPhone came to a different network I'd be all over that like, well, like a person that thinks AT&T is evil and hates sleeping with the devil.
That said, some of the peeps defending Verizon also beg a chuckle. Evil? No, not that I'm aware of. But super stellar league of awesome as many are implying? Uhhh, no, definitely not.
My sig other has Verizon with a (semi)smart phone, and I have AT&T with the iPhone. At home she can only make calls from the kitchen as her signal goes in and out, I get five bars of 3G anywhere in the house, in the basement, the barn, the garage. We leave the house and travel west she goes to analog then no service, I'm fine however. There is a bizarrre dead zone near where we live where I do go to EDGE for a bit, but otherwise fine. NYC where I'm from, in the city, full bars, but yes, dropped calls, but my friends there regardless of network complain about it. Think about it, big steel buildings in concrete canyons where you can't make sight-line with any cell array, many of which are tacked on buildings (ugly as that is), c'mon, get serious. And her Verizon drops calls in NYC same rate I do only I get a stronger signal.
So half of this "Verizon is teh godz herherher" is kinda overblown here. Decent I'm sure, sup0r awesome as some are saying? Uh, no, not hardly.
That said I'd welcome the option even though, sadly, with Verizon's spotty coverage all over upstate New York probably sadly would have to stay with AT&T until VERIZON got better service.