It took me 3 months to hit the HF EJB book, during which I also tried some application servers including "Sun's Application Server" and "JBoss."
I read the book 4 times with the EJB spec only for reference.
I think the book, together with EJB Plus simulator, is enough for the exam.
The IDE I used to test the application servers was JBuilder 2005.
Scott H. Kao