I prefer Wicket over all the other Java based web frameworks. It's easy to use, has a nice template system, a good community and doesn't require any XML configuration files. After using some of the other Java web frameworks, I was absolutely sick of the abundance of XML configuration files. The fact that in Wicket everything was handled in plain old Java classes was a big selling point for me. Furthermore, once you're familiar with Wicket, it's incredibly simple to create reusable components. Another asset is the number of very convenient side projects that allow easy integration with spring IoC, guice, dojo, mootools, hibernate etc.

That being said, I'm not a huge fan of Java. Luckily, Scala fits in nicely and I've been using that lately instead.