AT&T (now cingular) for about 20 years. Best coverage and products. Currently have a Nokia 6200 which is awesome and has one of the best OEM accessory suites I've ever seen and is super-hackable, plus it syncs with Outlook and talks to PDA's or laptops via IR. Getting ready to move to the 6230 though and my fiancee is taking the 6200. $60 plan gets me nationwide no-roaming, 1000 anytime minutes, unlimited nights and weekends starting 7PM, unlimited mobile-to-mobile, roll-over and a whole host of other nifty perks. Gotta love a competitive market!