Let me add by saying I'm a fan of the JCP.
Here's my scenario: I'm a graduating senior in college (CS) and I have been preparing for the Java Programmer exam. I am planning on taking the exam in the next few weeks. I've had a few people tell me that I'm wasting my time. However, I have not let them discourage me; for I feel I have learned A LOT during my preparation for the exam. Plus in the current job market I feel the certification can only help. I've been so happy with the learning that I've already picked up the SWCD book