Rating cellular service by customer turnover

It's not a great metric, since different contractual practices will produce different churn rates, but we really don't have much data to rate cellular service providers so churn may have to do:

AT&T Hoping the iPhone Has Coattails - New York Times

...AT&T is now losing around 1.7 percent of its subscribers each month, compared with 1.1 percent at Verizon. T-Mobile’s churn is 2.6 percent, while Sprint’s is 2.3 percent....

T-mobile and Sprint look pretty bad based on this metric and Verizon is in a league of its own.