Wifi... that's your workaround.

EVDO Rev. A supports simultaneous voice and data, but the big CDMA carriers (Sprint and Verizon) saw no reason to implement it as they were doing the Rev A upgrade. Now that AT&T is touting that as a major feature (keep in mind, AT&T has taken longer to get 3G up and running) there will be pressure for simultaneous voice and data in the future. It's coming, but the reason why we don't have it now is that there wasn't enough competition when they had the option to implement it.