I passed SCBCD last week with 95%. I studied specifically for the exam for approximately three months.
I used "Enterprise JavaBeans" by Richard Monson-Haefel in the preparations. I cannot say enough good things about this book and I highly recommend it to anyone who is preparing for SCBCD. It is easy to read, to-the-point and I think one of the most updated EJB books on the market (it covers EJB 2.1). It covers most of the topics you need to know for the SCBCD exam. Also, the book includes a JBoss workbook section with a lot of useful examples. I used JBoss and Ant when trying the examples in the book.
After studying this book for about two months going through Head First EJB for the final exam preparation was a breeze which took 4-5 days.
I used the SoftSCBCD exam simulator for the final preparations the last days before the exam. I scored between 85%-95% on the mock exams. The questions were very much like the questions on the real exam so I recommend it.