I was an AT&T customer (then cingular, and my wife has been on sprint, so I can do some side by side for you.

I too was Sprint, but in my few blocks of Manhattan they had no coverage, so I had to switch to something else.

Coverage - Both have their issues, there are places Sprint had a bad signal, and places Cingular had a bad signal. I wouldn't consider one better then the other.

Phones - I need to make and receive calls, so that's not an issue.

Customer Service - Whatever service you have at Sprint, it's going to be light years ahead of Cingular. They are the worst example of customer service on the planet I've seen in a very long time (you can tell I'm not happy with them).

Billing - We never had an issue with sprint at all. Cingular, for whatever reason, decided a few months ago to bill me for two calls just over six hours each, made at exactly the same time, and I'm still fighting to get that resolved. They refuse to work it out, and until I went to the BBB with it other state and federal agencies, all they did was to tell em to pay up or off to collection it goes.

I moved to a prepaid with tmobile, it's saving me a ton of money for my calling patterns, and it's been great.