I've recently picked up Spring Roo and decided to build out a web application using the framework. It is certainly a rapid development framework, up to speed with the other popular framework by Spring, Grails. What interested me the most with Roo though was the ability to easily plugin Spring-MVC, use multiple datasources for the Model, and to scaffold all the necessary JUnit test cases without me intervening.
In my use case, I wanted to utilize both structured and unstructured data, so I was able to easily define my Entities as belonging to either JPA or Mongo (my personal options). The only problem with this is that a single Maven module can only be setup with a single datasource using Roo, which can easily be resolved by using modules.