I had around 2 years of Programming exp in Java 1.4 prior taking the exam. Also I had done around 4 months of development work in the current company in Java 1.5, this helped me a lot.
K&B book, which I referred, was the most important step towards my success in certification.
The practice questions given at the end of each chapter are very helpful in testing your understanding. The most important thing is not to repeat the mistakes or forget the concepts that you learn while answering these questions.
I could not afford for commercial certifications. But mock exam by Marcus Green and the exam that comes with K&B CD was very helpful.
Finally, its better if you give enough time to prepare for certification instead of rushing for it(at least 2-3 months, if you have prior exp in Java. Well thats my opinion!!).
All the best for the folks who are preparing for it.