Wired recently conducted a series of international speed tests on the iPhone 3G and it looks like where you live greatly effects the performance you will experience. The test involved over 2,600 individuals and the results are rather telling.
 

At the moment, Australia has the slowest 3G download speeds, which averaged at 759 Kbps. However, the fastest speeds were held by individual carriers in Europe, such as European T-Mobile, which had an average speed of 1,822 Kbps. Canada came in second with Rogers and Fido performing at 1,330 Kbps.

However, AT&T came in third. They tied with Telstra, Telia and Softbank with an average speed of 990 Kbps. While 3G performance seems to be awesome in some areas and downright disappointing in others, AT&T, and therefore iPhone users, fall somewhere in the middle.

[via MacRumors]