True, it is difficult to revamp any system while it is still operating. AT&T certainly experienced a lot of customer dissatisfaction when they absorbed Cingular and were trying to upgrade as well as assimilate all at once. Even Nextel had a few issues (circa 2003) when Motorola was upgrading them to the 6X vocoder for increased capacity of their iDEN network, and again during the rebanding process after Sprint took over Nextel.

Still, Verizon seems to be able to consistently have the best network, with the fewest interruptions for any cause. If one company is doing a demonstrably better job at network upgrades & buildout (as Verizon consistently does), all of them SHOULD be able to do just as well. Sprint is just historically (& currently) weak in terms of field operations & network upgrades, so they botch more jobs than any other carrier, thus perpetuating Sprint's perception as a second-tier provider (compared to Verizon and AT&T).

Then there's the customer-experience side of it (separate from network performance) that Sprint has always struggled with...