I'm leaving AT&T as soon as the iPhone 5 comes out. AT&T's "4G" is more like Edge in Salt Lake. No matter how many bars I have with a 4G tag the slowness is unbearable. My daughter's 3G Verizon iPhone 4S is tons faster than my AT&T 4S.
Salt Lake City is on the list to get AT&T LTE soon. So you might want to stay with AT&T after all once you get an iPhone 5.
Doesn't matter how fast it is between the phone and the tower if AT&T throttles the speed from the tower to the 'net. If the problem isn't an intentional throttle, but tower oversubscription, why would I trust them to do LTE right? Either way, AT&T lost a customer.