what are some of the faults that AT&T has compared to Verizon?
From my experience and where I've lived with cell phones (OH, MA, NYC, SoCal), Verizon has much better coverage than AT&T. Dropped calls were not unexpected when I was talking to my friends with AT&T/Cingular Wireless, whereas with Verizon it's rare. That definitely depends on your region, and I understand there are places where AT&T is the best choice. I just haven't happened to have experienced any of them.
With 3G, a lot of those issues will be lessened, which is one of the reasons I finally made the jump.
I know this is a matter of personal opinion and experience, but I have had no complaints with Verizon's customer service in 11 years. There have been the ocassional snarky reps, but overall, I've had good experiences, and all of my issues have been addressed appropriately. I haven't always heard the same from Cingular/AT&T customers.
AT&T is lucky they're the ones who made the deal with Apple.

I know of between 8-12 people who, like me, wanted iPhones, but didn't want to switch to AT&T. I'm only the third to give in. Once Apple fixes a few more of the glitches/oversights, there will probably be a couple more. If Verizon had made the deal, people would have been switching and porting at even higher numbers than are happening now.