Hello,
The main advantages of using OSGi is component based and service oriented approaches to organize and modularize your applications during development. At this level, Spring DM provides facilities to use Spring within OSGi bundles and to add dynamics within dependency injection. Moreover, at runtime, you don't have conflicts any more between different versions of tools and your application administration is much flexible. No more need to stop the application to update it!
Regarding cool applications, you can find some in the Spring DM distribution and in the source of the book (
http://code.google.com/p/springdm-in-action/)
. For the later, you can see chapter 6 for application organization, chapter 7 for data access and chapter 8 for Web...
Hope it answers to your questions.
Thierry