According to an article on theiphoneblog, iPhone 3.0 GM (GM meaning Gold Master) features the on-device iTunes application now with TV shows, music videos, movies, audio books and iTunes U.
To make room for the extras the Top Ten and Downloads tabs at the bottom are lost and now have Video and a More icon, which allows access to a screen that gives iTunes U and Audio Books.
Much like the iPod application there is an Edit button which enables the dragging of icons to whatever customisation suits your needs, and as always 3G isn’t an option for anything over 10MB.