MegaNerd: These national plans require a tri-mode phone, but it isn't AMPS, TDMA and GSM/PCS. Cingular is GSM on the west coast and in parts of the SE, but is TDMA most other places. There are no tri-mode phones phones like you speak of on the market now - the trimode phones are 800 TDMA, 1900 TDMA and AMPS. GSM phones are 1900 MHz. Nokia and others are developing GAIT phones, the Nokia 6340 is one of them, that will make transition between GSM and the existing TDMA/AMPS network more seamless. These phones are necessary as Cingular converts to GSM, and for those that travel a lot. This is not required for the new national plans. If I take my Cingular TDMA phone to California, where Cingular is GSM, I would roam on AT&T. This roaming would be included in the national plan.
BTW Cingular service is very good here in Dallas 🙂