I passed the exam yesterday. Some background on my preparation. I started and finished a year long implementation cycle in EJB 3.0 for my current client. 2 years prior I had extensive Hibernate implementation experience. Before starting my studying campaign, I was very comfortable with JPA from hands-on experience and had developed Stateless, Stateful and MDB experience along the way. Following the implementation, I started studying in Dec 2007. It took 2 months to study in 3 bursts of weeklong effort. Burst 1 was reviewing the core principles by reading Headfirst EJB (EJB 2.1 spec). Burst 2 was a detailed review on Txn Propagation / Exceptions / Bean Lifecycle in mid January using the O'Reilly EJB3 book. Burst 2 was done by getting up very early in the AM (5:30) and reading until 7 AM with another pass at lunch time. Burst 3 involved shutting out all interruptions / obligations 4 days before the exam and covering the side issues (Web Services, Interceptors, Security, Timers).
It's a hard exam. You must absolutely understand the principles of distributed transactions to score reasonably well. Dont even think you can do the SCBCD if you've spent most of your time with Hibernate development. Hibernate developers who think the SCBCD is within reach might be very disappointed to find that the transaction processing semantics expected on the exam are often seldom-encountered the the typically stateless web applications that the Hibernate often finds itself employed within. They key to passing the SCBCD is to understand transaction propagation, as well as the risks and requirements you need to manage when you translate a business process requirement into a transaction scope and how those transactional resources cooperate with the container to meet the objectives.
As far as "high" scores on the Sun Exams ; I dont think high scores are a predictor to skill or ability competitiveness given my 83% despite extensive deliverables prior to the exam and 3+ years of JPA indicate anything substantial given that I've had extensive deliverables prior to the exam and my experience level is very good. There are two few questions, too little exam time available and too few cases to make a connection between high score and high ability. However, I do believe it is important to score WELL BEYOND the pass threshold to confirm your competence and preparation commitment.