Been waiting for this post...
1) Gapless playback, at least on the Zune.
2) Native DivX support. Xvid would be a nice bonus, but DivX is as must.
3) Support for embedded album art.
4) True out-of-the-box Drag-and-Drop support. I want to load up the Zune without using the Zune software.
5) A clock displayed on every screen that syncs the time with my desktop.
6) Hey, how about listing what freaking track number we're on?!! Seriously, $20 CD players have this function. While we're at it, show me of how many songs in the list we're talking about (i.e. track 5/12).
7) I would LOVE the ability to browse via Folder, rather than Artist or Album. I have all of my music arranged in nice little folders and I don't need to browse them in any other fashion.
8) I HATE the fact that the Zune picks up each and every 'contributing artist'. I have an entire entry for Coldplay, but the only 2 songs of theirs I have are on the Garden State soundtrack. I don't want them listed by themselves. If I had actual Coldplay albums, I'd be even more annoyed that it mixed them together...
9) It's a Microsoft product... Where's Solitaire and Minesweeper?
10) More file navigation options from within the Zune itself. In particular, I want the ability to delete files off my Zune when I'm done with them (like movies).
All of these are possible with a little (OK, maybe a lot) of firmware tweaking. However, if every single one of them were added, the Zune would be close to the perfect player (for me)...