According to an engineer who worked on the network/radio for the iPhone, there's a good reason Apple didn't have 3G in this iteration of the iPhone. He says less than 1% of Cingular customers have HSDPA capability—it's only available in a dozen or so markets. Plus, the engineer says the target users wouldn't know the difference anyway. Great confidence in the consumer, even if it's sorta true.
BUT, and this is the most important point, Apple's already designed a 3G version that's "in the works" with the FCC. 3G lovers may want to hold out for iPhone version 2.