Applicando published an interesting speed comparison video comparing the iPhone's EDGE download speeds and a mimicked 3G iPhone.
In the comparison video two iPhones load the same web page side-by-side. The 3G iPhone is demonstrated using a Wifi connection sharing the internet connection of an iMac which was connected to the internet via HSDPA (Huawei E172 HSPDA modem).
In the end the "3G iPhone" downloads the page almost twice as fast.