Motorola V600

I need help in selecting a phone carrier. I am torn between ATT, T-Mobile, & Cingular. I decided against Verizon because I do not like their phones. I want a national GSM plan. Can anyone shed some light for me? My main concerns are quality of service, knowlegable & helpful customer service, plan prices and phones. I want to get a phone similar to the qualities of the V300 or the Panasonic X70. Can anyone out there help me?? Anything help is greatly apprecieated.