I passed yesterday and here are some of my observations. I lurked on this board for a while and drank heartily from the generous measures of advice poured by the bartenders and regular posters. Thanks to all of you.
I used "Complete Java 2 Certification" by RHE as a study guide, and i really liked the book. I also did the mock exams at JavaPrepare and jchq which rounded out my knowledge a bit more. Do as many mock exams as you can.
I lost points by not knowing in depth some method signatures and class hierarchies. I don't generally try to learn this stuff off when it's readily available in the API but it's important for the exam. That's my one problem with certification exams.
To get a high mark, I would recommend knowing the following aside from the other main exam topics:
+ method signatures for all the main classes in java.io
+ method signatures for all the main methods in Math class
+ event class hierarchy, e.g. EventObject, and their associated listeners and adapters.
+ collection class and interface hierarchies
Also, a few obvious points worth repeating. Make sure you scroll down to see all the answer options for each question. The status bar tells you to scroll when necessary, but look at it especially if you don't fancy any of the current answers listed. Also, read each answer option carefully as it is easy to carelessly pick a wrong but similar answer because you're rushing. This may make all the difference between passing and failing.
I found the exam challenging, and definitely learned a lot from the experience. Good luck to anyone else plunging in soon.