I have found that JNDI works great, so you don't need the complexity of rmi-iiop. Currently, I tested it successfully with JBoss --> JBoss and WebSphere --> JBoss, although I had to include the JBoss client jar for WebSphere.
Basically, if your JNDI look internally was "MyApplication/MyBean", then your JNDI for remote lookup might be "jnp://remotehost:1099/MyApplication/MyBean". You can obtain any remote EJB interface this way so long as you can plug the host name or IP address for the remote server in the lookup string. I have the Web module grab this from a properties file. For EJB to EJB, you might grab the remote host or IP from a user updateable database entry.
Let me know if you need more details.
worked a treat.