Nathan blogged a while back about Ruby on Rails and which Java frameworks are best to compete with it. He tips Wicket as the best Java framework for this purpose, but still has some doubts on the statefulness of Wicket applications.
But since a week or two, Wicket has support (in CVS HEAD) for 'stateless' pages. It still needs testing, but Jonathan Locke has worked quite hard to make this possible. Wicket 1.2 will become a giant leap!