For me this is the best IDE so far to help me in my studies in Java Certification.
It helped me a lot with SCJP and SCWCD and still helps me a lot with the SCBCD.
Why ? Because I just download one package of the IDE, install and start coding the examples in the book and studying them...
With some other IDE you need to configure a heck lot of stuff... It drives you away from the fact that you NEED to study the technology and not be configuring it to suit your best needs. Let's face it... If you are studying already a certification is because you have little knowledge about a specific subject and you want to make it better.