I've been a silent spectator so far at java ranch but have thoroughly enjoyed reading the posts here. The certification results section is what kept me going and motivated me by reading people's post who passed the exam.
I gave my exam on Jan 9th and got 58/61 scoring 95%.
Here's what I did to prepare:
* Read K&B exam prep book 3-4 times, made my own notes for faster reviewing. I gave all the exams 2-3 times at the back of the chapters.
* I didn't try the mock exams until the last week and I did Marcus Green exams (all 3), the 2 master exams that comes with the K&B book, 2 other free mock exams and obviously Javaranch roundup of 144 questions. Infact I did K&B exam only 2-3 days before the exam and focused again on K&B back chapter exams and their CD exam. On the day before the exam, I went through my notes and the exam watch points in K&B book.
I never considered any other book or mock exams because I didn't want to overdo or overload myself. The exam is exactly as the book says, maybe simpler.
Before this book, I did read K&B Head First Java book and I must say I'm a fan of their series now. I've 4 books from them already, the latest being on design patterns.
I would say prep time was 2-3 months sporadically.