We demoed the Vaadin 6.2 already few weeks ago at the Vaadin Developer Meetup. Many active developers using Vaadin have already been trying out the 6.2 series snapshot before the official release. I'll explain what makes them so eager.
Your widgets - reusable
You have an idea for a web UI component. Simply use the new Vaadin Eclipse integration plugin to create fully functional template project and component (here is a short video). Implement your component in Java (only) and export it as a single jar-file. Reusing the component in other projects is just a matter of dropping the jar into your WEB-INF/lib!
Read the chapter 10.2. "Doing It the Simple Way in Eclipse" in Book of Vaadin for details.
While component distribution just made a giant leap forward, under the hood you still have the Vaadin's solid server-driven architecture combined with GWT based client-side richness.
New components and demos.
The biggest new feature is Portlet 2.0 (JSR-286) support. Other new features include UI enhancements like Tabsheet closing and better tree styling. In addition to these, we have upgraded The Vaadin Sampler to include more component demos and sample code for You.
Testing taken seriously
Although the next generation of Vaadin Testbench is not officially released yet, we are using it internally to test Vaadin itself. Our automated nightly tests include currently over 1500 screenshot-based tests running on 7 different web browsers and 14 server environments. And the number is growing!