What is it good for

It's supposed to help people run their Vaadin Applications easily in a OSGi Environment without the need for special Compendium Services.
Just plain OSGi

How does it work

Just some OSGi-Black magic for tracking bundles.
A tracker that watches for bundles importing com.vaadin and providing special Manifest headers.
And also taking care of bundles providing custom themes.
For each Application a HttpServlet is created which is registered as a Service.
For the std. /VAADIN/* context a special Servlet is created to take care of all the Themes needed.
This Servlet is informed of new Themes if those are installed.

So there is still some specialties needed?

Yes indeed, but just two.

declaring the application

Add a OSGi Manifest header to your Manifest called: Vaadin-Application
With this header you declare the Application instance to use.
Almost just like adding this property to the web.xml in a std. Vaadin War.

Vaadin-Application: org.pax.vaadin.samples.simple.app.MyVaadinApplication

declaring the alias

To address your application you still need a alias to retrieve it,
therefore another header for declaring the web-context is needed: Vaadin-Alias

Vaadin-Alias: /SampleVaadin

external dependencies?

Yes, Pax Web is needed and the Whiteboard extender and of course a Vaadin Bundle is needed also.

Any Samples

There are sampels available in the sources.