If you don't define the class it will use the startup class. If I understand the docs correctly :) 

http://help.eclipse.org/juno/index.jsp?topic=%2Forg.eclipse.platform.doc.isv%2Freference%2Fextension-points%2Forg_eclipse_ui_startup.html

Tried using a class similar to the svelto startup class but it didn't get invoked either :-/