I own 6 iPods, an iRiver Clix 2 and now a Zune 80 and here is what I think of the Zune after one week.

Pros

Navigation with twist interface much better than the interface on the new iPod nano’s and iPod classic. I can’t stand the split screen.
Brushed aluminum back: This is one of the best features, I own 6 iPods and I scratched every single one of them within 15 minutes of taking them out of the box and I baby my electronics!
Glass screen: another plus, all my iPods(save my iPod touch) I have scratched the screen within a week or so of owning them.
Zune pad: I love tactile feedback, my iPod touch is frustrating sometimes because it attracts smudges and fingerprints with all the “touching”. I also love being able to swipe to change a song or menu on the Zune.
Stock ear buds that are actually worth keeping/using
Wireless syncing was easy to setup and use but I seriously doubt I will ever use it.

Cons
Build quality is nowhere near the iPod. The Zune 80 feels toy like.
My Zune has frozen during use 3 times in the 5 days I have owned it which required a reboot( ala holding the back button down while pressing up on the Zune pad)
Zune software installation process. On Vista Home premium it took me over an hour to get the software installed(I work in the IT Field so this should have been a no brainer). Another hour to figure out how to get all my album art to show up on Zune 80(Erase all content and resync device after rebooting computer).
Zune marketplace software has been dumbed down way too much. Microsoft could have just cloned iTunes and it would look better and be a lot better laid out/organized.
Wifi sharing: I think it will be many years if ever that I find another person with a Zune that I can/want to “squirt” a song to.
Only works with Windows. Thankfully I now have a Intel Mac and am able to run Vista in Bootcamp. Before when I only had a Powerpc Mac I had to admire from afar. If they made the Zune cross platform I have a feeling more people would try them out.

In closing I enjoy the Zune 80GB and its interface over the new iPod Nano and iPod Classic, however it could use more advanced settings options, an equalizer, and the video playback needs some tweaking(When a video ends on the Zune it doesn’t do anything. On the iPod it kicks you back to the video menu.)