I got face time with a Zune this weekend and decided to look at how the form factor compares to the 80GB iPod I picked up a few days ago. The Zune weighs considerably less than the iPod, although I didn't have a scale on hand to get exact comparison. It felt like the Zune was more comparable to my Cingular 2125 phone, while the iPod weighs quite a bit more.
Screen size on the Zune is a slightly larger 3-inches, but you don't get a real sense for how much difference that makes till you see it next to the iPod screen.
Zune comes in just barely longer than the iPod.
iPod is slightly thinner than Zune, which makes the weight difference even more surprising.
Here's another variation on pairing the two devices.
Album art looks great on the Zune
Navigation through albums is highly intuitive, although you wouldn't know it from this photo.