Firstly, it showcases the excellent work the Dijit developers have put into new themeing skins. There are three themes completed so far, and changing the look of Dojo is now as simple as including a different CSS file on your web page. All Dijit widgets now run off a single CSS file, rather than each having their own CSS file.
Secondly, it shows the usage of many of Dijit’s widgets (say that five times in a row! :-) ). Many of the demos from the 0.4.* days are gone now, and this is about as comprehensive a demo of Dojo’s widgets as you’re likely to see for a while. And yes, they are very nice indeed.
Go to http://archive.dojotoolkit.org/nightly/dojotoolkit/dijit/themes/themeTester.html to see the default theme (tundra) in use. Click on the “Alternate Themes” tab at the bottom of the page to switch themes to one of the alternate themes.