3G performance is slow almost all over, especially in cities where the 3G service is getting overloaded. If you want to have fast speeds, hang out in Germany and the Netherlands -- those folks had the fastest speeds (and it's no coincidence that the 3G network there has three extra development years on its American counterpart). The worst reception is apparently in Australia, as Optus and Virgin users had their iPhones chugging along at just 759 Kbps.
What can we draw from this? Just like those Swedish scientists told us, it's the service, not the phone. But you know what Mark Twain said about statistics, so just in case you want to draw your own conclusions, Wired has kindly made a Google Spreadsheet of all the data available to anyone who wants it. Anyone want to try putting together that heatmap?