How is the Xbox One controller improved compared to the Xbox 360? This is a question that 105 Microsoft employees have spent 2 years answering. The team have tried a lot of things, including the ability to emit smells (seriously); but a video has been released explaining exactly what's been done.
Elimination of the battery pack 'bulge,' haptic feedback in each individual trigger, severely reduced latency, and a hardened screw-less structure for the hardest of 'gamer rage' throws. This controller sounds like it has it all; but that's something we'll find out when the Xbox One comes out this Christmas.
Fingers crossed they sort out the D-pad this time!