New features mentioned:
Improved store navigation, including persistent navigation menu.
Full window iTunes store. For times when that sidebar is just too much.
Previews from anywhere in the store -- don't have to drill down to preview.
iTunes LP includes lyrics, liner notes, video, photos and "more."
iTunes Extras. It's like DVD extras, but with iTunes. Not clear if it includes director's commentaries, but let's hope.
Genius Mixes. It's like Genius Playlists, but it plays forever like a radio station.
App management, letting you set up and arrange your home screens on the iPhone and iPod touch. You can drag and drop to move certain apps or whole pages of apps.
Home sharing enables file transfers between up to five local computers of songs, videos and even apps.
You can send items in the iTunes Store as gifts, add them to a wishlist, and publish them to Facebook and Twitter -- look who's getting all social all of a sudden!
Source : iTunes 9 bringing iTunes LP functionality, 'beautiful new look'
Screenies : Engadget
App management seems like the only useful feature, as far as I'm concerned