I have Idea 3.0.5 installed for daily production use and it's working just fine. Then I wanted to try the latest EAP:
I installed Idea EAP build 963 without JRE. Then I added Idea856 JRE package to the IDEA_HOME. I modified IDEA_SYSTEM_PATH to differ from the one that 3.0.5 uses in the idea startup script IDEA_HOME/bin/idea.sh.
Idea 963 starts up nicely and everything seems to be working except UIDesginer and CVS-support is missing. Also the plugin manager displays an error when trying to install any plugin: java.io.FileNotFoundException: bin/../plugins/simpleUML_b15A.jar (No such file or directory).
I even tried manually to put SQL query plugin jar-file in the plugins directory, however the plugin didn't load on idea restart.
There is nothing special in the idea log and plugin-directory has all the build-in plugins.