I am from the NY area, and I am now in Raleigh North Carolina and working on Cingular's network with no roaming charges with e-mail and full data service. On AT&Ts network in northern PA (along I-80) I was not getting data service or e-mail, just telephony.

I don't know if this means that when unlocked it will stop working on Cingular's network, but at least when locked on T-Mobile's network it works perfectly on Cingular's network.