Actually it appears that you are overlooking the fact that AT&T has added this ability to their EDGE network in many locations and as they upgrade their EDGE network it becomes available in more locations. Again, this depends on where you are in the country but there are many reports across the Internet of people being able to receive calls while downloading data.
Hmm, you misunderstood what I meant. EDGE suspends the data transfer while in a call. AFAIK UMTS doesn't.