Work is well underway towards 1.0.0.Beta21, including adjustments in how we use Maven to interact with Rubygem dependencies.
In previous versions, we'd used mkristian's extensions to Maven to allow it to treat rubygems.org as a normal Maven repository with a custom layout.
That failed to some extent, in handling missing dependencies and for synthesizing POMs from the gemspecs.
Now, though, we're using mkristian's gem-proxy, running at http://rubygems-proxy.torquebox.org/. It's not pretty at the moment, but for any gem hosted at rubygems.org, you can fetch back a Maven POM.
Like a POM for Rails 2.3.8.
Additionally, we've improved the RSpec plugin to make it easier to run single rspecs from the command-line against your JRuby projects.