i had cingular for all of a month before i switched to verizon..
they are terrible!
the customer service is unable to understand simple questions and are very rude and unwilling to help you.
my phone would cut off for no reason and my service would be out for hours at a time. i dont know if they were upgrading the network or something but i sure never saw the results of any upgrading.
the plans are also unflexible and a waste of money.