After buying the 3G iPhone, one of the first things I did with it (once it was activated) was to go to an area that I know is blanketed by AT&T's 3G network. In side-by-side comparisons, a Nokia N95 showed full 3G coverage, while the 3G iPhone gave me a "No Service" message. Um, excuse me?
Not only was the iPhone not connecting to AT&T's 3G network at all, but it wasn't even falling back on the EDGE network, either. The only way for me to get any sort of coverage or service at all in 3G network areas is to turn off the 3G radio. Only then will the 3G iPhone find and connect to AT&T's EDGE network. Performance like that pretty much negates the whole point of having the device.
When questioned, AT&T representatives say its network is performing wonderfully, and that any problems are hardware related. Apple hasn't responded to any complaints of poor radio performance.
I have conducted a full range of side-by-side comparisons. The Nokia N95, the Motorola Q9h, and the Samsung BlackJack II all give me full 3G strength in areas with good coverage. The iPhone? Nada. Zip. Zilch. No Service.