Microsoft Watch has posted a brief review of Windows Media Player 11. Here's a bit:

The first look at the Windows Media Player shows what looks to be a massively changed interface and for the most part it is. Like IE 7 and the upcoming Office 2007, Windows Media Player has switched from a predominantly menu based toobar to a menu free toolbar with large funtion buttons (though as in those applications the Classic Menus can be restored). The default toolbar buttons in Windows Media Player 11 are Now Playing, Library, Rip, Burn, Sync and Urge (a built-in link to the Urge online music store).

However, while the look of Windows Media Player has changed, much of the functionality and usability remains pretty much the same. I do like that when clicking one of the toolbar buttons I was presented with options specific to that task (such as ripping a CD) but then again, that's pretty much the way menus work. Navigation has been improved and sorting through your music collection is now easier in Windows Media Player. In general, most jukebox tasks are easier to do now in Windows Media Player 11.