Android on the carrier of your choice, hands down. My wife and I recently switched from a pair of iPhones to a Droid and HTC Incredible, respectively. Using our

Android on the carrier of your choice, hands down. My wife and I recently switched from a pair of iPhones to a Droid and HTC Incredible, respectively. Using our phones (and integrated Google Voice) is like a breath of fresh air. Between leaving AT&T, the customizability of the OS that my wife likes, and the developer freedom that I like, I can't imagine us making a better choice.