Karthik Guru has been using Wicket not too long, and is already enjoying it, and using quite some advanced features of the upcoming Wicket 1.2 release.
In his article Karthik works his way from a standard Wicket form to an AJAXified form that validates when the fields of the form loose their focus ('onblur'). The application then makes a validation AJAX roundtrip to the server and updates both the field component and the validation messages on the page.
Definitely worth a read when you want to catch up on the progress Wicket has made in this regard. I hope we can see more of these articles from Karthik and other users!