A 13-city mobile data speed test conducted by the serious wonks at PC World has validated results from a similar test by gadget blog Gizmodo in December.

“AT&T says it has worked hard to improve its much-maligned 3G network over the last eight months — erecting hundreds of new cell towers, using better-performing wireless spectrum, and souping up its cell sites across the country,” PC World reporter Mark Sullivan wrote. “The results of our latest 13-city 3G network performance tests suggest that the network has indeed undergone a drastic makeover.”

In spring 2009, AT&T delivered the lowest average download speeds in a 3G performance test by PC World. This month, Sullivan wrote, “AT&T’s download speeds were 67 percent faster on average than those of the other three largest U.S. wireless providers — Sprint, T-Mobile, and Verizon.”