For the most part, the new iTunes feels like the old iTunes. The experience is much faster though and has a decidedly more modern, streamlined user interface featuring flashy, colorful graphics. Apple has trimmed a lot of fat, but with so much information to present and sort through, navigation can still feel a bit convoluted, especially compared to minimalist services like Rdio.
As for the interface, gone is the left-hand navigation panel that used to permeate the experience. Now, you can toggle between the iTunes Store and your Library through a button in the upper right of the iTunes window.