Maven - the "Convention over Configuration" Disadvantage

The Maven approach reduces the JAR-file bloat that consumed most version-control repositories. But using Maven encourages you to adopt its "convention over configuration" approach to building software, which can limit your flexibility in customizing your build scripts.

http://www.ibm.com/developerworks/java/library/j-ap05068/

Workflow Defined

Workflow is the general way of linking services together

 http://www.nesc.ac.uk/technical_papers/UKeS-2004-05.pdf

Significance of the Mach Kernel

 Unlike traditional systems, under Mach a process, or "task", can consist of a number of threads. While this is common in modern systems, Mach was the first system to define tasks and threads in this way. ... The existence of ports and the use of IPC is perhaps the most fundamental difference between Mach and traditional kernels.

http://en.wikipedia.org/wiki/Mach_(kernel)

Singleton in the cluster

Even my device control JMX mbeans support high availability where they are automatically managed to run as a singleton in the cluster.
http://humbleblogger.blogspot.com/2005/04/aspnet-vs-j2ee.html

Message Persistence

Also, with async-style RPC there's no equivalent to message persistence - which when message persistence is coupled with transaction semantics, it enables messages to be reliably processed (think credit card transactions, etc).
http://humbleblogger.blogspot.com/2005/04/aspnet-vs-j2ee.html