AT&T and Cingular aren't really on "the same network". They have reciprocal agreements where towers that are run by one can be used by another in a form of roaming. AT&T runs more of the towers in the NE and Cingular runs more in the South. Cingular was the old "Cellular One" which got bought by SBC and became Cingular when BellSouth bought in.
Geek speak: Both AT&T and Cingular used TDMA (Time Division Multiple Access) while Verizon used CDMA (Code Division Multiple Access) for many years (CDMA is a little more robust, since you can fit more conversations into the same amount of space, especially if there are periods of "silence"). Both AT&T and Cingular have been changing over to GSM (used primarily in Europe), which is quickly becoming a standard here, and is more flexible than either TDMA or CDMA. It is also supposed to result in fewer dropped calls and allow for GPRS (for sending data).
I've had Cingular ever since it was Cellular One, and the only times I've ever had problems with the service was during 9-11 (cell towers down and busy in S. Manhattan) and the Blackout (Cell towers out and overloaded there too).
I can forsee some benefits to AT&T customers, especially those who use their phones as wireless modems, as AT&T didn't allow that in some locations.
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This message was edited by wilee on 2-18-04 @ 10:20 AM