The Zune has a central control wheel, just like the iPod, but it's smaller -- and it's not really a wheel. It's just five switches (left and right, top and bottom, and center) under a plain, unmarked black plastic disk that practically screams "cheap" -- it looks like it will have a chip out of the edge in four or five months. And those five switches don't quite do what you'd expect them to. There are two additional buttons to the right and left of the wheel that do most of the heavy lifting.
In fact, the Zune's operating interface feels more complicated than the iPod's. I'm clicking "Up" to get back to higher-level menus when I should be clicking "Back." I'm holding buttons down when I should just be clicking. In particular, the Zune misses the easy list-scrolling functionality provided by something like the iPod's scrollwheel or the BlackBerry's clickwheel.
On the other hand, the screen is big -- twice as large as a standard iPod -- and bright and beautiful. It obviously gave the Microsoft designers plenty of inspiration to reach into the eye-candy bag and sprinkle it on everything the Zune does.