Most people have said that hardware-wise, the Zune is actually a pretty good device. The problem was the interface software, which was clunky and hard to use. The new Zunes probably improved the hardware (the new hardware interface is said to be quite good), but the biggest improvement was a complete re-write of the Zune interface software, which makes the ability to copy media files to the player vastly easier.
Considering that the thing (original Zune) is a Toshiba Gigabeat S, the hardware should be good.
However, the placement of the controls is different and the unit is just awkward to hold in the hand and use. One handed operation can be physically painful because of how it is balanced.