To follow-up from Consumer Reports reader feedback, Verizon is the best overall across the largest number of metro areas. T-Mobile was also solid, and the handful of areas they had enough responses for All-tel had them rated very good. Cingular was OK, but they ragged on the support, and Sprint was the worst.
It's all pretty local though, so some schmuck-tel provider might be the best in a given area instead of one of the national players.