I have started a new project called asynchrmi. The purpose of this lib is to make it simpler to write serious applications that calls a JBoss application server.
We were in the process of writing a modern web frontend to our car-sharing system when we concluded that: 1) making many parallel calls to JBoss as different users didn't work, and 2) that because of the heavily relational datamodel (a typical Hibernate model) you needed to make several calls to get all the data you wanted - calls that could be parallelized.