When you read about AOP carefully, you must conclude that it will still be impossible to have different version of the same (AOPied) class within JBoss at the same time. This directly implies that all problems mentioned at http://www.jboss.org/thread.jsp?forum=92&thread=28964 remain UNRESOLVED.
I think AOP is a complex issue and an interesting idea and I will not juge about its benefits here. But I also see that it changes the feeling of the Java language to something more Smalltalk like. I also expect security issue to arise from AOP and feel that the original hierachical ClassLoader idea of Java is much more save for networked applications.
The main point is still that AOP is NOT COMPATIBLE WITH THE J2EE SPECIFICATION. ejb-2_0-fr2-spec.pdf, chapter 24.2.7, page 500:
"An enterprise bean?s remote home and remote interfaces are remote interfaces for Java RMI. The Container must ensure the semantics for passing arguments conforms to Java RMI. Non-remote objects must be passed by value. Specifically, the EJB Container is not allowed to pass non-remote objects by reference on inter-EJB invocations when the calling and called enterprise beans are collocated in the same JVM. Doing so could result in the multiple beans sharing the state of a Java object, which would break the enterprise bean?s semantics."
Of course this implies that different version of a class with the same qualified name must be possible if they are in different packed archives.