T-mobile has been my provider of choice for the past three years. They have great service and coverage where I am. I have to admit I'm a bit of a cell phone whore, I've got a SE T610, Samsung T509, Moto v600, Moto Razr V3, Moto e398... and a few others. I prefer the SE's to everything in their ability to sync with OS X nicer than any other phone. However, with that said, the Moto e398 is my favorite overall for design and hacka-ability.

Like you stated up above, the T509 is kind of quiet but I love it's thin figure.