Jon Udell has some initial thoughts (and more) as part of an article he is working on. He explores the pros and cons of using a J2EE container/EJB architecture for development.
This is something we have also been looking at for our enterprise software suite. Currently, we have taken a collection of open-source programs (SQLedger, OpenCRM, Ralata, DataVision) and made them work together with a common database (PostgreSQL) at the backend so that we have to Only Handle Information Once (OHIO).
We have been debating whether we need an Application Server layer. Am looking forward to reading Jon’s article.