I've had my 80GB Zune for just over a week now, and so far I'm pleased with my purchase. Not all is perfect, of course, but it's filling its role as a worthy successor to Gigabutt. One thing I like about it is what I personally call the "virtual trackball" that's used for navigation. The Zune uses a four-way directional click-pad that looks like a square with very, very rounded corners, almost to the point of it being a circle. To select a choice, you click down on the center of the pad. You can scroll through lists of songs by holding up or down on the pad, with the scroll-speed accelerating the longer you hold it down. Initially, there's nothing really extraordinary about this; it's the same mechanic used by many devices, including the Creative Zen and my old Gigabutt.
The fun comes in when you actually discover its touch-pad nature. The pad responds to the motion of your finger in the four cardinal directions. So, if you're navigating a list of songs and you slide your thumb down slightly, you'll scroll down a few songs. If you start your thumb at the top of the pad and briskly swipe it downwards, the list starts scrolling at a high velocity before grinding to a slow halt after a second or two. This feels remarkably like a trackball, so if you then start thinking about the pad as if it were a trackball (limited to four directions, of course), you'll begin to understand intuitively how to scroll through your lists.
For instance, if you roll a trackball downwards multiple times in succession, the ball will end up rolling for a good while without your assistance as a result of the momentum. These "physics" are applied to the touch-scrolling too: Swipe your thumb from top to bottom multiple times, and your song list will start scrolling incredibly fast -- with quick, subsequent swipes adding momentum -- before slowly stopping. So how do you keep yourself from overshooting where you want to be? Well, how would you stop a trackball? That's right -- put your hand on it. Likewise, as your songs are scrolling happily on their own, you can stop the scrolling just by laying your thumb on the pad. This is great, mostly "thumbs-off" approach for people scrolling through a small chunk who don't want to hold their thumb down or keep twirling it in a circle (a la the iPod's clickwheel) the entire time.
The flipside to this is that once in awhile, when you mean to click down on the center of the pad, your thumb ever-so-slightly moves in a direction. The pad could pick this up and inadvertently scroll to and select the item above or below the one you actually meant to click. It takes a little getting used to in order to over come this little snare.
It also would have been nice if the touch-pad registered diagonal directions for browsing photographs. When browsing by folder, the Zune spits out thumbnails of every picture in the folder in a grid format where you're free to navigate and choose. If you swipe in a diagonal direction, though, the cursor does this clumsy two-step -- "down, then right" -- instead of skipping diagonally to the picture. While this is functionally the same thing, it doesn't even always do that; it'll soemtimes stop after the first vertical or horizontal direction. Not a big deal by any means at all -- just a minor quibble, given how cool the "trackball" feel of the pad is.
Finally, I know some people like scrolling with the iPod's wheel. For those who don't mind keeping their thumb in constant motion, it offers the best control over your scroll speed. You can scroll precisely as fast as you want, and stop exactly when you want to. Seeing as the touch-pad on the Zune is so rounded, wouldn't it be cool if it emulated the scroll wheel -- for those who wanted such an option -- by responding accordingly to thumb movement around the perimeter (or circumference, if you please) of the pad? That might make it the most versatile input device for an MP3 player yet. As it is, however, it's still a lot of fun to use.