My experience with Cingular has been OK - sometimes good and never terrible. I was with ATT before and noticed that their customer service went through bad and worse patches.

My son broke his phone, and wife thought hers was broken (the settings had somehow magically re-set themselves, probably banging around in her purse).

Since I was with ATT, I could not upgrade phones without a new contract from Cingular. And they could not match the 4 line plan we have. But the fellow on the phone did some work arounds and we ended up with two very cheap Motorola replacements and kept the same plan. I have had other experiences when they have gone out of their way.