The Zune HD UX is godawful. Not only do you have to both press a button and interact with the touchscreen to play/pause, skip, or adjust volume, but the relevant button is on the opposite end of the device from the headphone jack. That means it's sitting upside down in your pocket and you have to reach into your pocket and past the bulk of the device just to adjust the volume.
The original Zune UX was a work of art by comparison. The buttons were on the face and recessed, so not only did they not get pressed accidentally, you could control your media right through the outside of your pants without even reaching into your pocket.
