The new file format gives you new features, like SmartArt Graphics.
The new file format also gives you the ability to use features that are available only in Word 2007. One example of such a feature is the new SmartArt Graphics.
The illustration here shows you how to start such a graphic in Word. Notice how many SmartArt Graphic designs are available to choose from.
The new file format supports plenty of other new features, such as math equations, themes, and content controls.