Zune is completely different - GUI-wise - from iTunes or WMP. It shares some GUI elements with WMC (which I also tore out of Windows 7, mostly because I never used it) but has two GUI modes. On the one hand, there is the screen that appears when you launch the program from its icon (ie without plugging the phone/Zune player in):

This is the "Quickplay" screen and it function as the media player. Clicking on any of the links in the upper left takes you to a different GUI. Here's the Collections tab:

I scrolled down to show two things - what the software does with unknown album/absent album artwork files and what happens to some, but not all, unicode file names (note Johann Pachebel... the rest of the name was in hangul EDIT: with the smaller pic sizes, you'll need to zoom into the image to see it) and yet it handles other unicode, for example the Chinese below. In this regard, it functions no differently than WMC/WMP/iTunes. I suspect it has to do with the tagging, but playing around with files in the past, I've discovered neither rhyme nor reason behind WHY this happens.

Selecting a file to play gives the player:

One the other hand, interacting with the phone looks like this:

All of the same tabs are available BUT they now refer to what is located on the phone. This is REALLY obvious because the name of the phone stays to the left of the screen and at the bottom is the graphic of a pc. If you click on that you go back to the collection stored on the PC.
I just tried to play a DVD using Zune but it looks like a no-go. DVD's files are not listed in the file types handled by Zune, so it looks like I'm going to be keeping WMP around


Sorry, my attempt to show the GUI is ham-fisted at best (I'm not good at this!) and my intention to show the two GUI modes discretely is an epic fail, but I hope you get the idea.
In sum, I haven't really used the software enough to form a definite opinion about it. It's no worse than iTunes; whether it is any better remains to be seen.
EDIT: uploaded more reasonably sized screenshots and clarified a couple of points...