ONJava has a review of Wicket. He concludes that Wicket is a good contender if you're looking for a component-oriented web application framework.
Timothy O'Brien has written about selecting a web application framework and continues to review different tools. His first impression of Wicket is:
It's different, in some ways refreshing, but like all web frameworks, it comes with a special set of problems. It's a little code heavy to be considered cool by the Web 2.0 crowd. But, at the risk of sounding like a Java developer, there's nothing wrong with writing compiled code now and then, and Wicket seems to make it easy to approach web application design from an OO "mindset".
After the common reaction of "do we need another framework", he goes through two different opinions. The first:
Wicket is an awful code explosion, written by Java-intoxicated programmers. ...In this age of lightness, Wicket is a heavy hammer. If you are looking for Hello World in 1 minute, run toward something else as quickly as you can.
After that strong negative reaction, O'Brien comes around to a even stronger positive reaction. He notes that it is a valid criticism to call it code heavy but maintains that not having to deal with markup more than makes up for it.
if you are looking for the Hello World in One Minute framework, there's a good chance that you are not developing a real application. Wicket brings complexity in the form of a rich component framework, but this complexity brings with it the ability to code a web site without having to code yet another table, or yet another paging mechanism. Believe it or not, the code you end up creating with Wicket is clean, and from what I've seen you don't end up making any compromises wrt to separation of presentation and logic.
InfoQ has covered Wicket in the past, when version 1.2 was released and a comparison with JSF and Spring MVC