Mine is the Samsung Dart. I'm thinking about switching to Verizon though and upgrading to a better phone. I don't need anything fancy, but I do need better reception because I live in the sticks. Not sure if Verizon will be any better, but I've heard they have very good area coverage.
I have AT&T. We've been with them for about 9 years now. Never had any real issues, but they're the only ones with consistent coverage.