If you want to proceed quickly from Hello World to a complex application, I suggest looking at Eclipse RCP, which uses SWT.  Whether it is suitable will depend on what kind of app you want to build.  Here's a list (with screenshots) of open-source apps that use Eclipse RCP:<p><a href="http://www.eclipse.org/community/rcpos.php" rel="nofollow">http://www.eclipse.org/community/rcpos.php</a>